1. Biology. Of, relating to, or forming a nucleus: a nuclear membrane.
2. Physics. Of or relating to atomic nuclei: a nuclear chain reaction.
3. Using or derived from the energy of atomic nuclei: nuclear power.
4. Of, using, or possessing atomic or hydrogen bombs: nuclear war; nuclear nations.

[From NUCLEUS.]

USAGE NOTE   The pronunciation (nū'kyə-lər), which is generally considered incorrect, is an example of how a familiar phonological pattern can influence an unfamiliar one. The usual pronunciation of the final two syllables of this word is (-klē-ər), but this sequence of sounds is rare in English. Much more common is the similar sequence (-kyə-lər), which occurs in words like particular, circular, spectacular, and in many scientific words like molecular, ocular, and vascular.

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.