a foot, afoot

A foot or a foot ( two words ) means one ( a ) part of the leg below the ankle, that goes in a shoe--
That opening should be too small for a foot to get stuck in.
These shoes won't do; a foot is either left or right.

A foot may mean the lower part of a table, or a machine part--
It's a foot from an old table, with a ball and claw.
It looks like a foot from an old sewing machine.

A foot or a foot also means one ( a ) measure of twelve inches ( foot )--
You'll need a board about a foot wide, and six feet long.
We'd like a foot long hot dog and a side of fries.

Afoot or afoot ( one word, rhymes with a foot ) means in progress or going on--
"The game is afoot."
There's mischief afoot.

Afoot may also mean walking, as a means of travel--
He came afoot, and needs a rest.
We can make twenty miles each day if we travel afoot.

Now that you know that, you can say--
"We have come ten miles afoot, and I couldn't go a foot farther."