which – lequel (m)/laquelle (f)
(Pronounced le-kell or la-kell)
To remember that which is pronounced le-kell or la-kell (lequel (m)/laquelle (f)) in French, use the following mnemonic.
Which kelp (quel) shall I have - the one served by the male (lequel) or the one served by the female (laquelle) waiter?

Note: Use lequel or laquelle according to the gender of the thing that is being referred to. When using lequel or laquelle, the thing being referenced must always have been mentioned previously in the same sentence, e.g. The horse which I bet on won the race (le cheval sur lequel j'ai parié a gagné la course.)
Examples of lequel/laquelle (which) in a sentence
Le pont sur lequel nous nous trouvons est le plus vieux de Paris.
(The bridge on which we are located is the oldest in Paris.)
J'ai plusieurs idées, sur lesquelles voulez-vous travailler?
(I have several ideas, on which ones do you want to work?)
La maison dans laquelle j'habite est assez petite.
(The house in which I live is quite small.)