- synaesthesiaA neurological or psychological phenomenon whereby a particular sensory stimulus triggers a second kind of sensation.
- syncytiumA mass of cytoplasm containing many nuclei; a multinucleate cell resulting from cell fusions of mononuclear cells (for example, the cells that make up animal skeletal muscle).
- sympatryThe use of the same (or overlapping) geographical areas, by populations of related species, without interbreeding.
- sympoiesiscollective creation or organization
- synclasticcurved toward the same side in all directions
- syncopateto omit a vocalic or consonantal sound or a syllable from a word; to use syncope
- syncrisisA figure of speech in which opposite things, people etc. are compared.