bases / basses are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
bases: (noun) installation from which a military force initiates operations. (noun) a place that the runner must touch before scoring. (noun) the bottom or lowest part. (noun) (anatomy) the part of an organ nearest its point of attachment. (noun) a support or foundation. (noun) any of various water-soluble compounds capable of turning litmus blue and reacting with an acid to form a salt and water. (noun) the bottom side of a geometric figure from which the altitude can be constructed. (noun) (numeration system) the positive integer that is equivalent to one in the next higher counting place. (noun) the place where you are stationed and from which missions start and end. (noun) the principal ingredient of a mixture. (noun) a flat bottom on which something is intended to sit. (noun) (electronics) the part of a transistor that separates the emitter from the collector. (verb) situate as a center of operations.
basses: (noun) the lowest part of the musical range. (noun) the lowest part in polyphonic music. (noun) an adult male singer with the lowest voice. (noun) the lowest adult male singing voice. (noun) the member with the lowest range of a family of musical instruments. (noun) nontechnical name for any of numerous edible marine and freshwater spiny-finned fishes.
bases: b·EY·s·ah·z
basses: b·AE·s·ih·z
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)