Here is a list of verbs that start with SI.
sickened, sickening, sided, sidesteps, siding
sidle, sidled, sifted, sigh, sighed
sighing, sight, sighted, sighting, sightseeing
sign, signal, signaled, signaling, signalizes
signals, signed, signified, signifies, signify
signing, signs, silence, silenced, silencing
silhouetted, simmer, simmered, simplified, simplifies
simplify, simulate, simulated, sin, sing
singed, singing, single, singled, singling
sings, singsonged, sink, sinking, sinned
sinning, sintered, siphoned, sipped, sipping
sired, sit, sits, sitting, situated
size, sized, sizzle, sizzled, sizzling
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