Be careful not to injure civilians! -Santa
Civilians are encountered on various missions in both The Operative: No One Lives Forever and No One Lives Forever 2: A Spy in H.A.R.M.'s Way. It is your job to protect them, as too many civilian casualties will lead to failure of your mission. In Scene 2 of Misfortune in Morocco civilians are targeted, forcing the player to react quickly and rescue the civilians to prevent mission failure. You can also interact with most civilians and sometimes they even give you useful information. Killing a civilian, either deliberately or not, will lead to instant mission failure, Civilians might cry out (out of fear) or react in any other way to anyone carrying guns and might alert enemy troops this way.
The word "civilian" goes back to the late 14th century and is from Old French civilien, "of the civil law". Civilian is believed to have been used to refer to non-combatants as early as 1829. The term "non-combatant" now refers to people in general who are not taking part of hostilities, rather than just civilians.
Civilian on Wikipedia