its not a silly question. dave is correct when talking about bicycles, but the bicycle industry measures chain "wrong"

in industrial applications chain is measured in number of pitches. an industrial engineer would tell you that a bicycle chain is 112 or 114 pitches long or 56-67 links. in this environment a "half link" for a bicycle chain would be a 1/2in section.

what a cyclist calls a half link would be referred to as an offset link:




why are these two environments different? i have no idea