In linguistics, function words (虚词) are words that have little or ambiguous meaning. Function words are mainly used to express grammatical relationships within a sentence or express the attitude or mood of the speaker. Content words (实词) are words that convey certain meanings. Whether a word can be an answer to a question is the simplest way to distinguish function words from content words. A content word can be an answer to a specific question. A function word cannot be an answer to a question (except “不”、“也许”、“没有”).