Subject-Verb Concord:
Subject-verb concord, also known as subject-verb agreement, refers to the grammatical rule that states that the subject and verb in a sentence must agree in number. In other words, a singular subject requires a singular verb, and a plural subject requires a plural verb.

- Singular subjects:
When the subject of a sentence is singular, the verb that follows it should also be singular. For example:
- The cat sleeps on the mat.
- She sings beautifully.

- Plural subjects:
When the subject of a sentence is plural, the verb that follows it should also be plural. For example:
- The cats sleep on the mat.
- They sing beautifully.

- Tricky cases:
Sometimes, there are certain words that may confuse the subject-verb agreement. For example:
- Collective nouns: Collective nouns refer to a group of people or things as a single unit. They are singular in form but can be singular or plural in meaning. The verb used with collective nouns depends on whether the emphasis is on the group as a whole or on the individual members. For example:
- The team is playing well. (emphasis on the team as a whole)
- The team are arguing among themselves. (emphasis on the individual members)
- Indefinite pronouns: Indefinite pronouns refer to nonspecific people or things. Some indefinite pronouns are always singular, while others are always plural. The verb used with indefinite pronouns depends on their singular or plural nature. For example:
- Someone is waiting for you. (singular)
- Some people are waiting for you. (plural)

Modals:
Modals, also known as modal verbs or auxiliary verbs, are a special type of verb that is used to express various functions such as ability, possibility, necessity, permission, and more. They are used together with the base form of the main verb.

- Common modals:
Some common modals include can, could, may, might, must, shall, should, will, would, and ought to. Each modal has its own specific meaning and usage.

- Examples:
- She can swim.
- He should study for the exam.
- They must finish their homework.

Determiners:
Determiners are words that are used before nouns to provide information about which person, thing, or group is being referred to. They help to clarify and specify the noun.

- Types of determiners:
There are different types of determiners, including articles (a, an, the), demonstratives (this, that, these, those), possessives (my, your, his, her, its, our, their), quantifiers (some, any, many, few), and more.

- Examples:
- The book is on the table. (definite article)
- This car is mine. (demonstrative)
- Some students are absent. (quantifier)

Tenses:
Tenses are used to indicate the time of an action or event in a sentence. There are three main tenses in English: past, present, and future.

- Past tense:
The past tense is used to describe actions or events that have already happened. It is usually formed by adding -ed to regular verbs or using irregular verb forms. For example:
- She walked to the store. (regular verb)
- They ate dinner. (irregular verb)