What is the most difficult thing about teaching a language?

Probably the most arduous task of language teaching is grammar. In my region, many students still struggle for instance, to conjugate verbs using the present continuous tense. In fact, some still treat all verbs as regular verbs that end with the morpheme -ed while deliberately ignoring the fact that there are irregular verbs whose structure is altered in their simple past forms. If such lingual incompetencies persist, then this problem will spread beyond structure rules and reach and affect writing so much so that it may render it logically illegible.

accent and pronunciation of words, followed by adaptibility in the native country

Arabic , Tagalog and Malayam ... because it’s very difficult to pronounce ... That’s the most thing to learn and teach ... Tnx

The use of the word in a more variable sense

The difficulty in teaching language is manipulation in the literal sense, which changes the meaning of sentence altogether

The grammar, the pronounciation of the word.and how to speak in a fluent way.

When teaching a second/other language to learners, I have found that the most difficult aspect is differentiating the learning material when there are drastically divergent skill levels in the smae classroom.  When you have students in the class who are brilliant and nearly fluent in the same space as students who cannot function well at all in the target language, it is highly problematic.

Finding ways to meet all students needs becomes nearly impossible under such circumstances.  In that situation, you try to reach the majority's needs (shoot for the middle), scaffold for the low level learners when possible, and keep a supply of extra activities (and peer tutoring measures) to keep the advanced learners occupied and engaged.

to be well informative with different vocabs and expressions and to be able to prounounce correctley as students will be learning from you  

We all have our own opinions of what makes learning a second language so difficult,so i think it depends on the person l’m teaching,and his/her ability to learn .

THere are several things but I think the most difficult is to repeat the same material over and over again many many times