fort, forte

Fort or fort means a strong and fortified place, occupied by troops, and surrounded by walls or other defenses--
The kids are building a pillow fort in the living room,  just like we used to do.
Our spies have learned that the enemy plans to attack our fort tonight.

Forte or forte ( usually pronounced "for Tay", sometimes pronounced to rhyme with fort ) means a strong point, or figuratively, an area of competence or expertise--
Leadership isn't his forte, but he's very useful in technical matters.
We have several voulunteer positions; what's your forte?

Now that you know that, you can say--
"Motivation seems to be his forte; his employees are convinced that the firm is a fort to be defended."

Note--"forty" means the number 40--
We'll be home in forty minutes.
Fifty minus ten equals forty.  [ 50-10=40 ]