Learn Hardcore Afrikaans: Sy sê dat sy ook sou hardloop, maar haar spiere is moeg. - She says that she would also run, but her muscles are tired.

The first sy (“Sy sê”) is the subject of the main clause (“She says”). The second sy in the subordinate clause (“dat sy ook sou hardloop”) is its own subject (“that she would run”).

What does dat do here, and can I leave it out like in English?

dat is a conjunction meaning that, introducing the reported clause. In Afrikaans you normally must include dat; unlike in English (“She says (that) she…”), you cannot drop it.

What does sou hardloop mean? Is this a tense?

sou hardloop is the conditional form, equivalent to English “would run.” It’s built from the modal auxiliary sou (the past-tense form of sal) plus the infinitive hardloop.

How is sou different from sal?

sal expresses a simple future: “will run.”
sou expresses a hypothetical or conditional: “would run.”

Why is sou (the finite verb) in second position in the subordinate clause, and hardloop at the end?

Afrikaans keeps a V2 (verb-second) order for the finite verb even in subordinate clauses when you use an auxiliary. Here the subject sy is first, sou (finite) is second, and the non-finite lexeme hardloop comes at the end.

What does ook mean, and could I move it?

ook means “also” or “too.” Adverbs like ook usually appear before the finite verb (sy ook sou…). You could say “sy sê dat sy sou ook hardloop,” but that shifts the emphasis (it highlights “also run” more than “she also said”).

What does moeg mean, and why say haar spiere is moeg instead of sy is moeg?

moeg means “tired.” By saying haar spiere is moeg (“her muscles are tired”), the speaker pinpoints physical fatigue in her muscles. If you just want to say she’s tired generally, you’d say “sy is moeg.”