Parts of speech are the building blocks of English sentences. They include nouns, pronouns, verbs, adjectives, adverbs, prepositions, conjunctions, and interjections. Each has a specific role, helping us structure sentences and express ideas clearly.

Sentence structure refers to how words are arranged to form meaningful sentences. It involves subjects, verbs, and objects, as well as how clauses are connected. Understanding sentence structure is essential for creating clear and grammatically correct sentences.

English tenses indicate when an action happens: past, present, or future. They help express time and the flow of events. There are three main tenses, each with four forms: simple, continuous, perfect, and perfect continuous.

Modal verbs (can, could, may, might, must, shall, should, will, would) express ability, permission, possibility, necessity, or advice. They modify the meaning of the main verb and are essential for conveying different attitudes or levels of certainty.

Conditionals describe possible outcomes based on conditions using "if." The four types are zero (facts), first (real possibilities), second (hypothetical), and third (past hypotheticals).

The passive voice emphasizes the action or receiver rather than the doer. It is formed using a form of "to be" plus the past participle (e.g., "The book was read by her"). It is used when the doer is unknown or irrelevant.

Gerunds are "-ing" verb forms acting as nouns (e.g., "Swimming is fun"). Infinitives are the base form preceded by "to" (e.g., "to swim"). Both can serve as subjects or objects, but their use depends on specific verbs and contexts.

Reported speech conveys what someone else has said without quoting their exact words. It typically involves changing the tense, pronouns, and time expressions (e.g., "She said that she was coming"). It is used to summarize or relay information indirectly.

Relative clauses give extra information about a noun, introduced by pronouns like "who," "which," or "that." They can be defining (essential) or non-defining (additional). For example, "The book that I borrowed is interesting."

Articles define nouns as specific or unspecific. There are two types: definite ("the") and indefinite ("a" and "an"). The definite article refers to a particular noun, while indefinite articles refer to any member of a group.