One half in French would be demi.
un et demi / une et demi
"une demi-soeur"
et demi
in football a cntre half would be 'un milieu de terrain' in French.
"mi-trimestre"
un demi
Demi-journées
demi-frère
"mi-trimestre"
In French, you would say "Il est quatre heures et demie."
how to say 1 sister in french is une soeur
demi frere