Dictionary.com

HII region

[ āchtōō ]
Save This Word!

A cloudlike region in space where the interstellar medium consists of ionized rather than neutral hydrogen. HII regions are centered around stars with very high surface temperatures and brilliant luminosities, whose radiant energy is sufficient to heat the interstellar medium to the point that hydrogen is ionized. The most conspicuous and best-known HII region is the Orion Nebula.
QUIZ
WILL YOU SAIL OR STUMBLE ON THESE GRAMMAR QUESTIONS?
Smoothly step over to these common grammar mistakes that trip many people up. Good luck!
Question 1 of 7
Fill in the blank: I can’t figure out _____ gave me this gift.

Words nearby HII region

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

How to use HII region in a sentence

FEEDBACK