week, weak

Week or week means a set of seven days--either from Sunday through Saturday, or any seven days--
I'll be back next week.
We have been busy at work all week.
School starts a week from tomorrow.
This will take me a week!

Weak or weak ( rhymes with week ) means having little or no strength or force--
He felt weak for days after running the marathon.
She talked so long that her voice became weak.
He never drinks anything stronger than weak tea.

Now that you know that, you can say--
"Working overtime all week left him weak and exhausted."

Note--"weaken" is the verb ( action word ) form of "weak"--
Poor nutrition will weaken your body.
"Weakened" is the past tense ( yesterday, or some time ago ) form of "weaken"--
Adding too much water weakened the tea.
His illness weakened him.
"Weekend" means the end of the week--Saturday and Sunday, when most people are not at work--
What are your plans for the weekend?
The weekend seems to be over in a minute. Now it's Monday already!
Note #2--"weakly" is the adverb ( describes an action ) form of "weak"--
"I feel okay"  she answered weakly.
"Weekly" means every week--
They planned to publish a new weekly magazine.
We get paid weekly.