Level 1 lesson 7 states that Pryd is used as a question and Pan in a sentence like I remember when.
However, in lesson 8 the statement is “I remember when you started to learn”. The answer was " galla i gofio pryd wnest ti ddechrau"
Should it not be " galla i gofio PAN wnest ti ddechrau?
are they interchangeable?
No, pan and pryd are usually not interchangeable, but in the given example, both work, although with (slightly) different connotations. As you said, pryd is normally used in questions, like “when is the next bus?” or “when were you born?” and so on, but it can also be used in “implied questions”. In a sentence such as
I can’t remember when the next bus is. you’d still use pryd: Dw i ddim yn cofio pryd bydd y bws nesaf, because you are talking about a specific time (and the subclause by itself would form a valid question).
But in sentences like “I remember when I was young” you are not talking about a specific moment in time, but the general circumstances, and in these you’d use pan: Dw i’n cofio pan o’n i’n ifanc (And you can never use pan in a question, implied or not)
So in this example both pryd and pan are possible, but with pryd you are talking about the specific moment in time, like the exact day the person started learning.
Yes pan and pryd can be confusing early on but usually makes sense later and that was a great explanation. Reminds me of a lovely song by Heather Jones ‘Dwi’n cofio pryd.’ - ‘I remember when’ (the time, date, moment).
Camgymeriad - ‘Rwy’n cofio pryd’.