Dragonball Complaints

[Super Buu]

According to 17/18's Wikipedia, it mentions it in the manga:

He is referred to in the original Japanese as an artificial human (Jinzoningen), which is translated as 'cyborg'/'android'/'robot'; he is not a robot nor an android, and it is implied in the manga he and his sister were originally runaway humans heavily fitted with cybernetics. As such, he is, in English, correctly a cyborg. Trunks also confirms this by using the word cyborg in the original version of the anime when describing to Goku about what the pair are that will ruin the future.

Also:

When Cell is defeated, Kuririn wishes for 18 to be turned into a full human. The Dragon is not able to do this, however, because she is not entirely mechanical, so Kuririn then wishes the bomb that is embedded within both 17 and 18 (which has near cataclysmic destructive power) to be removed as a compromise. Kuririn pursues 18 and him and 18 eventually have a child together, a daughter named Marron, a fact which confuses some fans, espousing the misconception she is an android.