max·il·la / makˈsilə/ • n. (pl. max·il·lae / makˈsilē; -ˈsilˌī/ ) Anat. & Zool. the jaw or jawbone, specifically the upper jaw in most vertebrates. In humans it also forms part of the nose and eye socket. ∎  (in many arthropods) each of a pair of mouthparts used in chewing.

maxilla
1. In vertebrates, the posterior bone of the upper jaw, which bears the teeth other than the incisors. The term is sometimes applied to the whole of the upper jaw.

2. In some Arthropoda, one of a pair of mouth-parts used in eating. The maxillae are paired, limb-like structures located immediately behind the mandibles, which articulate with the head capsule. See also MAXILLARY PALP.

maxilla (pl. maxillae)
1. One of a pair of mouthparts in insects, crustaceans, centipedes, and millipedes. They lie behind the mandibles and their lateral movements assist in feeding. Crustaceans have two pairs of maxillae but in insects the second pair are fused together forming the labium.

2. One of a pair of large tooth-bearing bones in the upper jaw of vertebrates. In mammals they carry all the upper teeth except the incisors.

maxilla (maks-il-ă) n. (pl. maxillae)
1. (loosely) the upper jaw.

2. either of the pair of bones contributing to the upper jaw, the orbits, the nasal cavity, and the roof of the mouth (see palate).
—maxillary (maks-il-er-i) adj.

maxilla jaw, jawbone. XVII. — L. maxilla, corr. to māla cheek, as axilla shoulder-blade to āla wing.
Hence maxillary XVII.