Choose the right word
keen, acute, astute, penetrating, perspicacious, sharp, shrewd
A knife can be sharp, even keen, but it can't be astute. While keen and sharp mean having a fine point or edge, they also pertain to mental agility and perceptiveness. You might describe someone as having a keen mind, which suggests the ability to grapple with complex problems, or to observe details and see them as part of a larger pattern ( a keen appreciation of what victory would mean for the Democratic party) or a keen wit, which suggests an incisive or stimulating sense of humor. Someone who is sharp has an alert and rational mind, but is not necessarily well grounded in a particular field and may in some cases be cunning or devious ( sharp enough to see how the situation might be turned to her advantage). An astute mind, in contrast, is one that has a thorough and profound understanding of a given subject or field ( an astute understanding of the legal principles involved). Like sharp, shrewd implies both practicality and cleverness, but with an undercurrent of self-interest ( a shrewd salesperson). Acute is close in meaning to keen, but with more emphasis on sensitivity and the ability to make subtle distinctions ( an acute sense of smell). While a keen mind might see only superficial details, a penetrating mind would focus on underlying causes ( a penetrating analysis of the plan's feasibility). Perspicacious is the most formal of these terms, meaning both perceptive and discerning ( a perspicacious remark; perspicacious judgment).