Meaning ‘together’, ‘with’

synsymsyl
idiosyncrasy
idiosyncratic
synagogue
synapse
synchronise (US synchronize)
synchronous
syncopate
syndicate
syndrome
synechdoche
synergy
synonym
synthesise (US synthesize)
synthetic
asymptote
symbiosis
symbiotic
symbol
symbolise
symmetry
sympathy
symphonic
symphony
symptom
symptomatic
syllabic
syllable
syllogism