Many animal species rely on internal fertilizations to successfully reproduce in terrestrial environments.

After medical school, she decided to specialize in internal medicine because she enjoys diagnosing complex chronic conditions.

The International Auxiliary Language Association, founded in 1924 to study the establishment of an international auxiliary language, presented Interlingua to the public in 1951 by publishing the Interlingua–English Dictionary and the Interlingua Grammar.

Many historians still refer to International Working Women's Day when discussing early labor movements.

We decorate the break room with skull-and-crossbones banners and serve rum cake every International Talk Like a Pirate Day to get into the spirit.

I received a notice from the Internal Revenue Service about an adjustment to last year's tax return.

Modern cars still rely on the internal combustion engine for most long-distance travel.

The selectors picked an experienced bowling attack for the one-day internationals next month.

Humanitarian aid teams reached remote camps where thousands of internally displaced persons were living in makeshift shelters.

Environmental regulations worldwide are pushing manufacturers to reduce emissions from internal combustion engines.