Translation of "opposite" into Latin

For every action there is always an equal and opposite reaction.

Actioni contrariam semper et aequalem esse reactionem.

It was stationed at an island opposite to Massilia.

Hae ad insulam, quae est contra Massiliam, stationes obtinebant.

There was much talk of every kind on the subject, and it was argued before the emperor with vehement opposition.

et studiis diversis apud principem certabatur adseverantium non adeo aegram Italiam ut senatum suppeditare urbi suae nequiret.