contacts
1)*predominant usage of the word* Contact lenses, AKA small pieces of plastic (which these days are usually pretty soft, as compared to the older, stiffer "hard" contacts) which are basically stuck on your eyeball as a replacement for glasses.  They have grown in popularity in the last several years, to the point where many people have them because they 
a)find them better than glasses
or b)think they'll look cooler without their glasses.
Watching people put in contacts is rather gross, and some people will tell you they hurt a lot or aren't worth all the trouble they cause.  But many others love having contacts and would never go back to wearing glasses.
2) people you contact for information (similar to sources)
1) My friend just got contacts cause he was sick of his glasses.
2) My contacts within the agency told me that the president was planning to unleash a new program soon.