attention, inattention

Attention or attention means notice or consideration, or mental concentration --
Raise your hand to get her attention.
Please pay attention; this is important.

Attention is also a military command, meaning to stand up straight and look forward --
Company, attention!
Remain at attention until you hear him say "at ease".

Inattention or inattention means neglect, or failure to notice or consider --
His inattention in matters of dress makes prospective employers wary.
He shows up for class, but his inattention is obvious.

Now that you know that, you can say --
"He is failing because of his inattention to lectures; when he pays attention he's a good student."

Note --"attentions" is an old-fashioned term meaning courting behavior --
He's been paying his attentions to the young widow next door.

attention, a tension

Attention or attention ( one word ) means mental concentration or consideration--
May I have your attention please.
He seems to have a short attention span; we'll have to work on that.

A tension or a tension ( two words, rhymes with attention ) means one ( a ) straining or stretching under force or pressure ( tension ) , physically or psychologically--
The machine just needs a tension adjustment.
This is supposed to be good for a tension headache.

Now that you know that, you can say--
"This cable may snap under a tension that's too much for it, so pay attention."