1. Case - a form of noun, pronoun, or adjective
Grammatical case is the way a noun, pronoun, adjective, participle or numeral is modified to perform a certain function in a clause or sentence. Linguistic term for this form of modification, which reveals the function of the word, is inflection. The English language has a limited case system, which is why some people whose native language is English may find learning languages such as Slavic or Baltic languages, which all have a developed case system, difficult. Cases in English are used in pronouns. For example, I is the nominative case, me is the accusative case, and my is possessive (often referred to as genitive).
2. Mood - a form of the verb in the English language
Verb moods indicate the attitude of the speaker. In English, there are three moods: indicative, imperative, and subjunctive.
Indicative mood is used in most statements and questions. For example: She loves cats. What does he do in his free time?
We use imperative when making requests and demands. For example: Close the door. Please take a seat.
Subjunctive mood is used in hypothetical or contrary-to-fact statements. For example: If she studied, she would pass the exam. As demonstrated by the example, these statements consist of two clauses: the if-clause and a clause containing the consequence of the action described in the if-clause.
3. Number - singular or plural forms of words
Verbs in English, like nouns, have two numbers: singular and plural. When the verb is in the singular form, it describes an action performed by one person or thing. If it is in the plural form, it refers to actions performed by more than one person or thing. A verb must agree with its subject in number. In linguistics, this is called subject-verb agreement.
4. Person - changes in pronouns or verbs to show the speaker
Besides the number, the verb has to agree with its subject in the person, as well. To reveal who the speaker is, we must use an appropriate pronoun and verb form (person). In English, there are six different persons:
I - first-person singular:You - second-person singular; He/she/it - third-person singular;We - first-person plural;You - second-person plural;They - third-person plural.
5. Tense - a form of the verb which shows time
Verbs tenses give us information about when the action represented by the verb is taking place: in the past, present, or future. To describe the things that have already happened we use the past tense. The present tense describes things that are happening right now or continuous actions. We use the future tense while talking about things that have not happened yet, but will at some point. English has a very complex system of tenses, and it's considered that there are 12 major tenses that every English speaker should know.
