Which prefix means 'not' typically used before consonants?

• A. Endo-
• B. An-
• C. Infra-
• D. A-

Answer: (D)

The key concept is negation prefixes in medical terminology and how pronunciation shapes their form. The prefix meaning not or without is a-, and it is the form typically used before consonant-starting roots to ease pronunciation and preserve a smooth word flow. You can see it in terms like asymptomatic (not showing symptoms), asocial (not social), and amorphous (without a defined shape). An- is the variant used before vowels to avoid awkward consonant-vowel transitions, as in anemia or anesthesia. Endo- means within, and Infra- means below, so they do not convey negation. Therefore, the prefix that means not and is typically used before consonants is a-.