Rationale comes
from Latin ratio, meaning "reason," and rationalis, "endowed
with reason." Ratio is reasonably familiar as an English word for the
relationship (in number, quantity, or degree) between things.
Congenial. According to ancient mythology, each person at
birth was assigned a guardian spirit. The Latin name for this attendant spirit
was genius. Two people who get along well together can be thought of as sharing
a similar spirit. They might even be described by a word combining the Latin
prefix com- (meaning "with, together") and genius—in English
congenial.
Exasperate means "to cause
irritation or annoyance to someone" or "to excite the anger of
someone." Exasperate comes from
Latin exasperare, whose base, asper, means "rough." A relative of
asper is asperity, which can refer to the roughness of a surface or the
roughness of someone's temper. Another is spurn, meaning "to reject."