Bases

Another classification of morphemes puts them into two classes: basses and affixes. A base morpheme is the part of the word that has principal meaning. Bases are very numerous and most of them in English are free morphemes ; but some are bound, like -sent in consent, dissent, and assent. A word may contain one base and several affixes.
A basis is a linguistic from that meets one or more of these requirements:

• It can occur as an immediate constituent of a word whose only other immediate constituent is a prefix or suffix.Example : react, active, fertilize

• It is an allomorph of a morpheme which has another allomorph that is free form. Example : depth, wolves.

• It is a borrowing from another language in which it is free a form or a base.Example : biometrics, microsoms, phraseology.