acr/acu

sharp; bitter

Spelled acr, acu, acerb · Latin acer 'sharp, pungent', acuere 'sharpen', and related acerbus 'bitter, harsh'

Latin acer meant 'sharp': acrid smoke bites the nose, acerbity sharpens a remark, and acumen gives the mind an edge.

Words built from it

acute — sharp, intense, or keenly perceptive
Latin acuere (sharpen) → acutus (sharpened, pointed) → acute
acrid — having a strong, unpleasant smell or taste
Latin acer, stem acr- (sharp, pungent) + English -id (adjective ending), modeled on acid
acrimony — bitterness or harshness in speech or feeling
Latin acer, stem acr- (sharp, bitter) + -monia (quality) → acrimonia (sharpness)
acerbity — sharp bitterness in manner, speech, or taste
Latin acerbus (bitter, harsh), related to acer (sharp), + -itas (quality) → acerbitas, through French
exacerbate — make a problem or unpleasant condition worse
ex- (intensive) + Latin acerbus (bitter, harsh) → exacerbare (irritate, make worse)
acumen — the ability to understand situations and make good judgments
Latin acuere (sharpen) → acumen (a point, sharpness)
acuity — sharpness of perception or thought
Latin acuere (sharpen) → acutus (sharp) + -itas (quality) → acuitas

acrobat — From Greek akros (high, at the top) + bates (walker). It uses a different acr-, not Latin acer or acuere.