7+3視覺英語網上英語課程，請問其中的 +3 （syntax）是講什麼？

Reference to the book referred by you TW Chen's the heart of grammar, you should make note that indep=co-or; indep=m.c.; dep=sub.. Herebelow are the identified website fuller definitions of Ah Tao explaining 3 syntax terms:-eg:- Compound sentence:-Main clause + 1 or more co-or(ind) clauses Complex sentence:-Main Cl.+ 1 or more sub(dep) clauses Compound-complex sentence:-m.c.+ 1 or more co-or clauses+1 or more sub cl.