four-and-a-half
UK[ˌfɔːr ən ə ˈhɑːf]US[ˌfɔr ən ə ˈhæf]
adj
Being equal to four plus one half; 4.5
n
The number or quantity that is four and a half
Etymology
The phrase is a straightforward construction from native English elements. "Four" derives from Old English fēower, from Proto-Germanic fedwōr, ultimately from the Proto-Indo-European root kʷetwóres. "Half" comes from Old English healf, meaning "side, part", from Proto-Germanic halbaz. The structure "X and a half" is a common pattern in English for expressing a number plus a fraction, with "a" functioning as a weakened form of "one". The entire phrase functions as a lexicalized unit to denote the specific quantity of 4.5, used both adjectivally and nominally.
Analysis
This is a fixed, idiomatic compound phrase formed from the cardinal number "four", the conjunction "and", the indefinite article "a", and the noun "half". Each element retains its standard English meaning and grammatical function.
Examples
The child is four-and-a-half years old.
Cut the recipe down to four-and-a-half cups of flour.
She finished the race in four-and-a-half minutes.