The Wonderful Si in Esperanto (Si, Sin, Sia)

Priskribo

Alex Vaughn Miller sings through a quick lesson about the reflexive pronoun si.
Here is a link to Alex’s latest book, The Marriage of the Muffin Man:
https://www.amazon.com/dp/1093879157/

This is a parody of the song “Under the Sea” from the Walt Disney film The Little Mermaid.
Here are the main things to know about si:

1) Si is only used in the third-person (so we don’t use it when talking about me, you, or we).
2) Si is required whenever it belongs in a sentence and is not just an optional way of being more specific.
3) Si can never be a part of the subject (so you can say “Li kun sia frato venis” but you cannot say “Li kaj sia frato venis” because the first puts it into a separate prepositional phrase whereas the second uses sia as part of the subject).
4) You can only use the word si after a preposition (al si, kun si, inter li kaj si, por si, per si, etc.).