To render acute in tone.
Sharp at the end; ending in a sharp point or angle: opposed to blunt or obtuse.
Sharp or penetrating in intellect; possessing keenness of insight or perception; exercising nice discernment or discrimination: opposed to dull or stupid: as, “the acute and ingenious author,” Locke.
Manifesting intellectual keenness or penetration; marked or characterized by quickness of perception or nice discernment: applied to mental endowments and operations: as, acute faculties or arguments.
Having nice or quick sensibility; susceptible of slight impressions; having power to feel or perceive small or distant objects or effects: as, a man of acute eyesight, hearing, or feeling.
Keen; sharp; intense; poignant: said of pain, pleasure, etc.
High in pitch; shrill: said of sound: opposed to grave. See acute accent, below.
In pathology, attended with more or less violent symptoms and coming speedily to a crisis: applied to a disease: as, an acute pleurisy: distinguished from subacute and chronic.
A mark (′ ) used to denote accentual stress, and also for other purposes. To denote stress in English, it is now generally placed after the accented syllable, as in this dictionary, but sometimes over the vowel of that syllable. The latter is done regularly in such Greek words as take this accent, and in all Spanish words the accentuation of which varies from the standard rule. In some languages it is used only to determine the quality or length of vowel-sounds, as on e in French (as in été), and on all the vowels in Hungarian; and in Polish and other Slavic languages it is also placed over some of the consonants to mark variations of their sounds. For other uses, see accent, n.
Keen may be the most objective of these words. An acute answer is one that shows penetration into the subject; a keen answer unites with acuteness a certain amount of sarcasm, or antagonism to the person addressed; a shrewd answer is one that combines remarkable acuteness with wisdom as to what it is practically best to say.
Shrewd differs from acute and keen by having an element of practical sagacity or astuteness. Only keen has the idea of eagerness: as, he was keen in pursuit. See astute and sharp.