Something on a body part

Question

Hi there,When speaking about an object or something being on a body part, do we always use "à"+le/la/les?example: " ...une plaie immense au bras gauche".What does it mean if you say  ".... une plaie immense "sur" son bras gauche"

Accepted Answer

Hi Ash,
As you will already be aware, prepositions often don't match their English equivalent.
In this case -
avoir une plaie à une partie du corps = to have a wound on part of your body 
uses 'à' in French and 'on' in English

j'ai une plaie au front = I have a wound on my forehead
j'ai une plaie à la hanche = I have a wound on my hip
j'ai une plaie à l'œil = I have a wound on my eye

it works like avoir mal à which is in the following Kwiziq lesson -
https://french.kwiziq.com/revision/grammar/avoir-mal-a-to-be-in-pain-to-hurt-somewhere
Bonne Continuation!