Active voice: A sentence where the subject performs the action stated by the verb.

Affix: A word element that can be attached to a base or root to form a new word or new form of the word, usually occurring as either a prefix or suffix.

Auxiliary verb: A verb that occurs with a main verb (that provides semantic meaning to a sentence) and adds functional or grammatical meaning to the clause in which it appears. It is used to express tense, aspect, modality, voice, emphasis, etc.

Clause: The smallest grammatical unit that can express an incomplete proposition and typically consists of a subject and predicate.

Competence: Grammatical competence refers to the knowledge we have of a language that accounts for our ability to produce sentences in a language by using a rule in the interpretation, expression, or negotiation of meaning.

Conditional mood: A sentence used to speculate about what could happen, what might have happened, and what we wish would happen. It contains both an if clause (condition) and a main clause. Negative conditional sentences may use the word "unless" instead of "if".

Declarative sentence: A sentence that makes a statement and may be simple or complex. It does not ask questions, make commands, or make statements with emotion.

Defining clause: A clause that is not separated from the rest of the sentence by commas or parentheses and is used to tell which specific person or thing is being talking about within a larger group of people or things. The meaning of the sentence will change significantly if it is removed. (e.g. "The weather that we had this summer was beautiful.")

Dependent clause: A clause that provides a sentence element with additional information, but cannot stand alone as a sentence. It can either modify an adjacent clause or serve as a component of an independent clause. (e.g. "When we arrived at the airport...")

Descriptive grammar: A set of rules about language based on how it is actually used and there is no right or wrong language.

Determiner: A word placed in front of a noun to make it clear what the noun refers to. Determiners include other types of words definite and indefinite articles, demonstratives, distributives, numbers, and difference words.

Direct object: The person or thing that receives the action performed by the subject of a sentence. (e.g. The cat played with the ribbon.)

Exclamatory sentence: A sentence that is used to express strong feelings or emotions or for emphasis.

Fragment: A group of words that does not express a complete thought.

Future continuous tense: A sentence that includes a verb to indicate that something will occur in the future and continue for an expected length of time. It includes the simple future of the verb "to be" and the present participle (i.e. a verb ending in -ing). (e.g. "I will be watching the game tomorrow.")

Future perfect tense: A sentence that refers to a completed action in the future. It is used this to project ourselves forward into the future and to look back at an action that will be completed some time in the future. It uses the simple future of the verb "to have" (will have) and the past participle of the main verb and usually uses a time expression. (e.g. "Will you have completed left the house before I come home from work?")

Future perfect continuous tense: A sentence that refers to events or actions that are currently unfinished but will be finished at some future time. It is used to project ourselves forward in time and to look back. It uses the future perfect of the verb "to be" (will have been) and the present participle of the main verb (base + ing) and usually uses a time expression. (e.g. "He will have been studying in university for eight years when he graduates next month.")

Gerund: A verb that is made into a noun by adding -ing. It retains properties of a verb, such as being modifiable by an adverb and being able to take a direct object.

Imperative mood: The imperative is used in commands and instructions. Imperatives in the affirmative are formed with the infinitive of the verb (without to), while negative imperatives are made with the infinitive together with do + not. The imperative doesn't typically have a subject. It’s used to order or ask someone to do something, to offer advice or encouragement, to give instructions, or to make suggestions. (e.g. "Read your book.")

Independent clause: A clause that can stand on its own and does not need to be joined to any other clauses because it contains all the information necessary to be a complete sentence. It has a subject (i.e. it tells the reader what the sentence is about), it has an action or predicate (i.e. it tells the reader what the subject is doing), and it expresses a complete thought (i.e. something happened or was said).

Indicative mood: The indicative mood is used to make factual statements, ask questions, or express opinions as if they were facts. It also can be used to state, ask, or deny a fact. However, it can also express an opinion because opinions are often stated as facts; when you have an opinion about something, you usually view it as a fact. It is the most common mood used in English and the simple, progressive, and perfect tenses all express indicative mood. (e.g. "Dogs make wonderful pets.")

Indirect object: A noun or pronoun that indicates to whom or for whom the action of a verb in a sentence is performed. (e.g. She bought her son a new toy.) If a sentence has an indirect object, it will always come between the verb and the direct object.

Infinitive: A combination of words made up of the word "to" and a verb in the simple tense. It can be used as a noun, adjective, or adverb. It is not a verb so it cannot be modified by adding -s, -es, or -ed.

Interrogative mood: The interrogative mood is used to ask questions.

Mixed conditional: A conditional sentence where the if clause and main clause refer to different times. It may refer to the present result of a past condition (e.g. "You wouldn't be in trouble f you had told the truth." or the past result of a present or continuing action (e.g. "I would watched the movie with you if I had known that you like Harry Potter.")

Modal verb: A verb that is used to express the belief that something is certain, probable, or possible. (e.g. might, could, etc.)

Mood: In grammar, mood is used to refer to a verb category or form which indicates whether the verb expresses a fact (the indicative mood), a command (the imperative mood), a question (the interrogative mood), a condition (the conditional mood), or a wish or possibility (the subjunctive mood).

Morpheme: A meaningful linguistic unit consisting of a word (such as dog) or a word element (such as the -s at the end of dogs) that can't be divided into smaller meaningful parts.

Non-defining clause: A clause that is always set off from the rest of the sentence with commas or parentheses and is used to provide more detail about the person or thing that is being talking about. The overall meaning of the sentence will be retained if the clause is removed. (e.g. "The owner of the cafe, who lives down the street, is a big soccer fan.")

Noun clause: A dependent clause that acts as a noun. (e.g. "what you see")

Noun phrase: A phrase that consists of a noun or pronoun (called the head) and any dependent words before or after it that give specific information about it. Noun phrases can refer to a particular example of something or to a whole class of people or things. (e.g. the brown dog)

Participle: A form of a verb that is used in a sentence to modify a noun, noun phrase, verb, or verb phrase. It is partly verb and partly adjective. They are often used as simple qualifying adjectives in front of nouns. (e.g. "The weathered shed remains unoccupied.")

Passive voice: A sentence where the subject is acted upon by the verb.

Past participle: A participle that contains the endings -ed or -d when used with regular verbs and -t, -en, or -n when used with irregular verbs. It is used to indicate a past or completed action or time.

Pedagogic grammar: A description of how to use the grammar of a language to communicate, for people wanting to learn the target language.

Performer: The person or thing that does the action in a sentence.

Past continuous tense: The past continuous describes actions or events in a time before now that are unfinished or incomplete. It uses the past tense of the verb "to be" (was/were), and the base of the main verb +ing. It can be used to do the following: to talk about something which continued before and after another action (e.g. "I was doing my homework when my sister got home."), to talk about something that happened before and after a particular time (e.g. "She was attending classes in the spring."), to show that something continued for some time (e.g. "Her hand was hurting."), to talk about something that was happening again and again (e.g. "My parents were always arguing."), and with verbs which show change or growth (e.g. "The city was expanding rapidly.")

Past perfect tense: A sentence that refers to a time earlier than before now. It is used to make it clear that one event happened before another in the past. It uses the past tense of the verb to have (had) and the past participle of the main verb. (e.g. "He had been working on an assignment when he was called for dinner.")

Past perfect continuous tense: A sentence that is similar to the present perfect continuous, but references a time earlier than before now. It uses the past perfect of the verb to be (=had been) + the present participle (base+ing). (e.g. "I had been working on an assignment when I was distracted by my text message.")

Past simple tense: The past simple tense is sometimes called the preterite. It is a sentence that is used to describe a completed action in a time before now. The time of the action can be in the recent past or the distant past and action duration is not important. (e.g. "I went to the post office yesterday.")

Predicate: The part of a sentence that modifies the subject in some way. It must contain a verb explaining what the subject does. (e.g. He was fixing the vacuum.)

Preposition: A word or set of words that indicates location (e.g. in, near, beside, on top of) or some other relationship between a noun or pronoun and other parts of the sentence (e.g. about, after, besides, instead of, in accordance with).

Prescriptive grammar: A set of rules based on how people think language should be used.

Present continuous tense:  The present continuous of any verb is composed of two parts—the present tense of the verb to be + the present participle of the main verb. It can be used to describe an action that is going on at this moment (e.g. I am doing my homework.), to describe an action that is going on during this period of time or a trend (e.g. Are you still working on your PhD?), to describe an action or event in the future (e.g. He is going to graduate next fall.), to describe a temporary event or situation (e.g. I normally stay home on Fridays, but I am going to meet my friend for coffee and dessert later tonight.), and with words like "always, forever, constantly", to describe and emphasise a continuing series of repeated actions (e.g. You are always ignoring my texts!).

Present participle: A participle that contains the ending -ing. It can be used as part of the continuous form of a verb (e.g. I am working.), after verbs of action or position (e.g. I go running every morning.), after verbs of perception (e.g. I saw the squirrel running along the fence.), and to explain a reason (e.g. Knowing that her daughter would be home in an hour, she left the door unlocked.)

Present perfect tense: A sentence that is used to indicate a link between the present and the past. The time of the action is before now but not specified, and is more interested in the result than in the action itself. It uses the appropriate form of the auxiliary verb to have (present tense), plus the past participle of the main verb. (e.g. Have you read all of the books in the Harry Potter series?")

Present perfect continuous tense: A sentence that is used to refer to an unspecified time between 'before now' and 'now'. The speaker is thinking about something that started but perhaps did not finish in that period of time. He/she is interested in the process as well as the result, and this process may still be going on, or may have just finished. (e.g. "He has been reading that book all day.")

Present simple tense: A sentence that is used to describe habits, unchanging situations, general truths, and fixed arrangements. It just uses the base form of a verb. (e.g. "He watches every Jets game on tv.")

Reference grammar: A description of how a language works that focuses on how it is used rather than rules.

Relative clause: A part of a sentence that adds meaning but is not essential to the sentence functioning grammatically.

Simple future tense: A sentence that refers to a time later than now, and expresses facts or certainty. (e.g. "It will snow tomorrow.")
 
Subject: The person, place, thing, or idea that is doing or being something in a sentence.
 
Subjunctive mood: The subjunctive mood is used to express suggestions, recommendations, advice, demands, wishes, and doubts. It is also used to talk about hypothetical situations or something that is contrary to fact.The present form of the subjunctive is most often used to talk about recommendations, suggestions, advice, requests, and demands, and it often (but not always) follows the word that. (e.g. "It was suggested that students complete an assessment before registering for the program.")

Tag: A grammatical structure in which a declarative or an imperative statement is turned into interrogative fragment. (e.g. "You like dogs, don't you?")

Type 1 conditional: A sentence that is based on facts and refers to a possible condition and its probable result. The if clause (i.e. condition) is in the present simple tense and the main clause is in the future simple tense. The type 1 conditional is used to make statements about the real world, and about particular situations. The time is the present or future and the situation is real. It is often used to give warnings. (e.g. "If I don't study, I will fail the test.")

Type 2 conditional: A sentence that is not based on facts and refers to an unlikely or hypothetical condition and its probable result. The if clause (i.e. condition) is in the past simple tense and the main clause is in the present conditional or present continuous conditional tense.These sentences are not based on the actual situation. In type 2 conditional sentences, the time is now or any time and the situation is hypothetical. (e.g. "If you went to bed earlier you wouldn't be so tired.")

Type 3 conditional: A sentence that refers to an impossible condition in the past and its probable result in the past. The if clause (i.e. condition) is in the past perfect tense and the main clause is in the perfect conditional or perfect continuous conditional tense. These sentences are truly hypothetical and unreal, because it is now too late for the condition or its result to exist. As a result, there is always some implication of regret with type 3 conditional sentences. (e.g. "If you hadn't lied to me before, I would have believed you."

Voice: The voice of a verb describes the relationship between the action (or state) that the verb expresses and the participants identified by its arguments (subject, object, etc.). When the subject is the agent or doer of the action, the verb is in the active voice. When the subject is the patient, target or undergoer of the action, the verb is said to be in the passive voice.

Zero conditional: A sentence that contains an if clause (i.e. condition) and a main clause (i.e. result) and both parts are in present simple tense. The zero conditional is used to make statements about the real world, and often refers to general truths, such as scientific facts. In these sentences, the time is now or always and the situation is real and possible. (e.g. "If you read a lot, you increase your vocabulary.")