The difference between Brace and Couple

Brace as a noun (obsolete):

Armor for the arm; vambrace.

Brace as a noun (obsolete):

A measurement of length, originally representing a person's outstretched arms.

Brace as a noun:

A curved instrument or handle of iron or wood, for holding and turning bits, etc.; a bitstock.

Brace as a noun:

That which holds anything tightly or supports it firmly; a bandage or a prop.

Brace as a noun:

A cord, ligament, or rod, for producing or maintaining tension.

Brace as a noun:

A thong used to regulate the tension of a drum.

Brace as a noun:

The state of being braced or tight; tension.

Brace as a noun:

Harness; warlike preparation.

Brace as a noun (typography):

A curved, pointed line, also known as "curly bracket": { or } connecting two or more words or lines, which are to be considered together, such as in {role, roll}; in music, used to connect staves.

Brace as a noun:

A pair, a couple; originally used of dogs, and later of animals generally and then other things, but rarely human persons. (The plural in this sense is unchanged.) In British use (as plural), this is a particularly common reference to game birds.

Brace as a noun:

A piece of material used to transmit, or change the direction of, weight or pressure; any one of the pieces, in a frame or truss, which divide the structure into triangular parts. It may act as a tie, or as a strut, and serves to prevent distortion of the structure, and transverse strains in its members. A boiler brace is a diagonal stay, connecting the head with the shell.

Brace as a noun (nautical):

A rope reeved through a block at the end of a yard, by which the yard is moved horizontally; also, a rudder gudgeon.

Brace as a noun (UK, Cornwall, mining):

The mouth of a shaft.

Brace as a noun (UK, mostly, in the plural):

Straps or bands to sustain trousers; suspenders.

Brace as a noun (plural in the US, singular or plural in the UK):

A system of wires, brackets, and elastic bands used to correct crooked teeth or to reduce overbite.

Brace as a noun (soccer):

Two goals scored by one player in a game.

Brace as a verb (transitive, intransitive):

To prepare for something bad, such as an impact or blow.

Brace as a verb:

To place in a position for resisting pressure; to hold firmly.

Brace as a verb (nautical):

To swing round the yards of a square rigged ship, using braces, to present a more efficient sail surface to the direction of the wind.

Brace as a verb:

To stop someone for questioning, usually said of police.

Brace as a verb:

To confront with questions, demands or requests.

Brace as a verb:

To furnish with braces; to support; to prop.

Brace as a verb:

To draw tight; to tighten; to put in a state of tension; to strain; to strengthen.

Brace as a verb:

To bind or tie closely; to fasten tightly.

Couple as a noun:

Two partners in a romantic or sexual relationship.

Couple as a noun:

Two of the same kind connected or considered together.

Couple as a noun (informal):

A small number.

Couple as a noun:

One of the pairs of plates of two metals which compose a voltaic battery, called a voltaic couple or galvanic couple.

Couple as a noun (physics):

Two forces that are equal in magnitude but opposite in direction (and acting along parallel lines), thus creating the turning effect of a torque or moment.

Couple as a noun (architecture):

A couple-close.

Couple as a noun (obsolete):

That which joins or links two things together; a bond or tie; a coupler.

Couple as an adjective (informal, US):

Two or (a) small number of.

Couple as a verb (transitive):

To join (two things) together, or (one thing) to (another).

Couple as a verb (transitive, dated):

To join in wedlock; to marry.

Couple as a verb (intransitive):

To join in sexual intercourse; to copulate.