A French word may be a basic word, like English soft, or a word with a prefix and/or a suffix, like presoftened and softly. These two words are part of a family of words that have the base word soft. In a family of words, the base word is the common element and contains the main idea of the word. Knowing the meaning of the base word (soft) and the meanings of the prefix (pre-) and the suffixes (-en, -ed, and -ly) helps you recognize or infer the meaning of a word like presoftened or softly.
To know the meaning of an affixed base word requires that you be familiar with the possible meanings of prefixes like pre- and suffixes like -ly. Fortunately, most French prefixes have recognizable English counterparts. Suffixes, however, differ quite a bit between French and English and require careful study.
A prefix is a letter or group of letters affixed to the beginning of a base word to add to or otherwise modify the base word’s meaning. For example, the adjective amoral is composed of the base word moral and the prefix a-, which adds the concept of not to the meaning of the adjective. The word moral means being concerned with right and wrong; the word amoral means not being concerned with right and wrong. A prefix does not change the function of the base word: moral and amoral are both adjectives.
A suffix is a letter or group of letters affixed to the end of a base word to form a new, related word. For example, the suffix -ity added to the base word moral changes the adjective moral to the noun morality. A suffix may change the function of a word; for example, fear is a noun, but fearful is an adjective. Some French suffixes are grammatical, including endings to mark infinitives, present participles, past participles, and adverbs. These suffixes and their uses are explained in Appendix A.