1.4 always...never
quotiēns, how often; totiēns, so often
semper, numquam nōn, perpetuō, always, constantly
plērumque, ferē, generally, usually; quod ferē fit, as generally happens
vulgō, generally, commonly
saepe, persaepe, often; saepissimē, saepenumerō repeatedly, again and again
crēbrō, often (of a regular sequence)
trītus, common, commonplace, hackneyed
nōnnumquam, sometimes (fairly often)
interdum, quondam, subinde, identidem, occasionally, now and then, repeatedly
aliquandō, on certain occasions, sometimes (not often)
rārō, rarely
singulāris, rare, remarkable
semel et saepius, plūs quam semel, more than once
semel, once
umquam, ever; numquam, never; nec umquam, and never
q.v. custom, usual, unusual 49.1
from A Handbook of the Latin Language by Walter Ripman (1930). Transcribed by Carolus Raeticus (2011).