How would we symbolize the following English sentence logically?

Question

Only a knight can marry my daughter. [ K(x): x is a knight; M(x, y): x can marry y; d: my daughter ]

I have tried to create some equivalences and identities, but none of them seem to be correct.

Answer 1

$M(x, d) \implies K(x)$.

If $x$ marries $d$ then $x$ is a Knight.

You can throw in some quantifiers if it will make you feel better.

Answer 2

You can do this with set notation:

Let $\mathbb{P}$ be the set of the population, and let $\mathbb{K}$ be the set of knights and $\mathbb{M}$ be the set of those eligible to marry the daughter be subsets of $\mathbb{P}$

Then $\mathbb{M} \subseteq \mathbb{K}$

Answer 3

"Only a knight can marry my daughter." $\equiv$ "If anything can marry my daughter, then it is a knight."