Prepositions

'in' or 'to' + country/state/region/city

For country:

• en + feminine countries.
  
• au + masculine countries.
  
• aux + plural countries.

For regions / states / counties:

en + feminine regions/states/counties

dans le (or dans l' in front of a vowel) + masculine regions/states/counties

au + Texas and Nouveau-Mexique

For city:

• à + city
• à la or au + city with an article

'dans' versus 'en'

Dans (+ article) is more precise (more physical/less general) than en.

en classe = in class.
dans LA classe = in THE class.


habiter + dans la rue/l'avenue
habiter + la rue/l'avenue
habiter + rue/l'avenue

All three are acceptable.

être/vivre + dans la/le + rue/avenue/boulevard, etc
être/vivre + rue/avenue/boulevard, etc

"se promener + sur l'avenue" = sur is only acceptable with avenue and with se promener

Transport:

 à + "individual" modes of transport (walking, bicycle, bike etc)
 en + "group" modes of transport (bus, coach, car, subway, etc)

These are acceptable:
par le + trains
par + planes

à vélo
en vélo

Compound nouns

 à = what something is designed for
e.g. un verre à vin = a wine glass.


de or en = what something is made of
e.g. un sac de cuir / un sac en cuir = a leather bag.


à la / à l’ / au / aux = what food is ‘made with’ or ‘flavoured with’
e.g. une glace à la vanille = vanilla ice cream.