This article lists various levels of differences between Hindi and English.
Alphabet: The Devangari script employed by Hindi contains both vowels (10) and consonants (40) and is characterized by bars on top of the symbols. Hindi is highly phonetic; i.e. the pronunciation of new words can be reliably predicted from their written form. This is in strong contrast to English, with the result that Hindi learners may struggle with English spelling. Conversely, they may mispronounce words that they first encounter in writing.
Phonology: In comparison with English Hindi has approximately half as many vowels and twice as many consonants. This leads to several problems of pronunciation. One difficulty is distinguishing phonemes in words such as said / sad; par / paw; vet / wet, etc. Words containing the letters th (this, thing, months) will cause Hindi learners the same kind of problems that they cause most other learners of English. The phoneme // as exemplified by the s in pleasure is missing in Hindi and so pronunciation of such words is difficult. Consonants clusters at the beginning or end of words are more common in English than Hindi. This leads to errors in the pronunciation of words such as straight (istraight), fly (faly), film (filam).
Compared to English Hindi has weak but predictable word stress. Learners therefore have considerable difficulty with the irregular stress patterns of words such as photograph / photographer. Hindi learners are disinclined to 'swallow' unstressed syllables such as the first syllables in the words tomorrow, intelligent, remember, etc., and will often try to clearly articulate short, common words that are usually weakly stressed in English: has, and, was, to, etc.
English, of course, is prevalent in India, and for this reason Hindi learners may well be extremely fluent. Nevertheless, native-English speakers often have difficulties understanding them because of the combination of the pronunciation problems listed above and the use of Hindi intonation patterns. (In Hindi emphasis is accomplished by higher pitch rather than by the heavier articulation that typifies English.) The result of this is the sing-song effect that English spoken by Hindi learners often has on native-English speakers.
Grammar - Verb/Tense: Hindi has tenses that similar those used in English: present simple, past continuous, etc., but there is a lack of correspondence in their use to express various meanings. This leads to the very common overuse by Hindi learners of the present continuous when in English the present simple is required: I am always playing golf on Sundays. / I am not knowing the answer.
Since Hindi does not have the auxiliary do, learners are prone to asking questions by means of intonation alone: She has a brother? and to making mistakes such as When you got married? or She not eat meat?
In Hindi the future tense is required in the dependent clause of conditional 1 sentences. This leads to interference mistakes such as: If you will help me, I will help you.
Grammar - Other: Hindi typically uses a subjunctive in polite requests, which have the word order of statements rather than questions. Interference results in problematic requests such as: You will tell me the time please, or You may lend me your dictionary.
There is no definite article in Hindi, and the number one is commonly used where in English the indefinite article is needed. As to be expected, these differences make it difficult for Hindi learners to get the articles right in English.
There are two aspects of word order that are different in Hindi and English. Firstly, the standard word order is in Hindi Subject-Object-Verb as against Subject-Verb-Object in English. Secondly, in Hindi the preposition comes after the noun or pronoun it qualifies (i.e., it is more correctly called a 'postposition'. There does not seem to be undue interference between the two languages in these areas. However, in common with most learners of English, Hindi native-speakers have problems with the correct choice of the English preposition itself. Mistakes such as They were sitting on (at) the table are typical.
Vocabulary: Hindi has incorporated numerous English words, which is a help to the beginner who quickly wants to acquire a large vocabulary. However, the pronunciation of many of the loan words has changed in Hindi. The interference this causes can lead to Hindi learners not being comprehensible when they use the words in oral English.
Understanding the differences helps as to train adult learners on english by getting to root of problems and contraints they face while acquiring a second language.
Can the experts add some more to these??