There is a connection between the native language of an ESL/EFL learner and particular difficulties in learning and using English and the kind of mistakes a learner typically makes in English pronunciation, grammar and vocabulary as there is native language interference in learning and using English.
Listening comprehension and speaking in English are the skills generally more frequently used than reading and writing in daily living in an English speaking country. Listening comprehension and speaking in English are more difficult and more important for learners to master than reading and writing. When reading and writing a text a learner has more time for thinking and pauses than when listening and speaking in English in daily living.
An ESL/EFL learner can also look up unknown vocabulary in English dictionaries and use other English reference books when reading and writing a text in English, which is impossible when listening and speaking in English. Therefore, listening comprehension and speaking in English are more difficult than reading and writing. English vocabulary for daily living requires more time and is more difficult to master by foreign learners than English grammar.
Vocabulary is one of the most comprehensive and difficult aspects of English for foreign learners to master thoroughly. They should first concentrate on learning the most frequently used and therefore most important English vocabulary for their practical real life needs.
Multiple sense English words and synonyms (words with a similar meaning) present special difficulty for foreign learners. Other difficulties in learning and using English vocabulary include fixed word collocations, phrasal verbs, idioms, proverbs and regional differences in vocabulary usage. There are differences in English usage in English-speaking countries in terms of spelling, pronunciation, vocabulary and grammar.
English usage can also be formal and informal. Formal English is the language of the mass media, education, business, economy, commerce, technology, science, etc. Informal English includes colloquial, slang and dialect usage. It is harder for foreign learners to master informal than formal English vocabulary.
English synonym dictionaries combined with general English dictionaries are an excellent tool for intensively, comprehensively and logically mastering vocabulary for the needs of the learner in real life situations. Extensive reading on a variety of topics is another effective method for expanding English vocabulary knowledge by learners of English.