hey !
i agree with syrian ... while i wanna add :
Nahw = to Syntax in English .. which means the way words are put together in a language to form phrases, clauses, or sentences.
Sarf = to morphology in English .. & it concerns with the patterns of word formation in a particular language, including inflection, derivation, and composition.
hmmm ... while for TAJWEED * : It is one of the Islamic Law sciences that are related to the Glorious Quran.
The word Tajweed linguistically means ‘proficiency’ or ‘doing something well’. It comes from the same root letters as the word ‘Jayyid’ in Arabic (meaning ‘good’): Jeem, Waw and Daal. When applied to the Quran, it means giving every letter of the Qur’an its rights and dues of characteristics when we recite the Quran and observing the rules that apply to those letters in different situations. We give the letters their rights by observing the essential characteristics of each letter that never leave it. And we give them their dues by observing the characteristics of each letter that are present in them some of the time and not present at other times.
& The knowledge of tajweed is contingent on four matters:
1. Knowledge of the articulation points of the letters
2. Knowledge of the characteristics of the letters
3. Knowledge of what rules change in the letters due to the order of letters
4. Exercising the tongue and a lot of repetition.
and yes , its preferred to mix sarf and nahw in tajweed teaching because of the vastness of the Arabic language, any small mistake in pronunciation of a letter or word may change the meaning of that word.