A1 used before nouns to refer to particular things or people that have already been talked about or are already known or that are in a situation where it is clear what is happening（用于名词前，指听者或读者已知的事物或人，尤指已提到的或能被领会的事物或人）

A1 used before some nouns that refer to place when you want to mention that type of place, without showing exactly which example of the place you mean（用于某些名词前，表示泛指一类地方）

A1 used before noun phrases in which the range of meaning of the noun is limited in some way（用在带有限制性定语的名词短语前）

A1 used to refer to things or people when only one exists at any one time（指独一无二的事物或人）

A2 used before superlatives and other words, such as "first" or "only" or numbers showing something's position in a list, to refer to only one thing or person（用于形容词或副词最高级及表示排名的词前）

used to say that the particular person or thing being mentioned is the best, most famous, etc. In this use, "the" is usually given strong pronunciation（用于表示“最…的”，此时 the 应重读）

used before some adjectives to turn the adjectives into nouns that refer to one particular person or thing described by the adjective（用在形容词前，指特定的人或事物）

used before some adjectives to turn the adjectives into nouns that refer to people or things in general that can be described by the adjective（用在形容词前构成名词，泛指一类人或事物）

used before a singular noun to refer to all the things or people represented by that noun（用在单数名词前，指该类事物或人）

used before a family name to refer to two people who are married or to a whole family（用在姓氏前表示某夫妇或一家人）

used before some nouns referring to musical instruments or dances to mean the type of instrument or dance in general（用在乐器或舞蹈的名称前表泛指）

used before a noun to represent the activity connected with that noun（用在名词前表示与名词有关的活动）

B2 used before numbers that refer to periods of ten years（用在逢10的数字前）

B2 used before each of two comparative adjectives or adverbs when you want to show how one amount gets bigger or smaller in relation to the other（用在两个形容词或副词比较级前，表示“越…越…”）

used before comparative adjectives or adverbs when you want to show that someone or something has become more or less of a particular state（用在形容词或副词比较级前，表示某人或事物的特定状态的变化）

used for emphasis when you are expressing a strong opinion about someone or something（用于强调所持看法）

B1 used instead of a possessive adjective such as your, her, or my（用于代替 your，her，my 等词）

enough足够的

each; every每个