Grammar - Verb/Tense: Arabic has no verb to be in the present tense, and no auxiliary do. Furthermore, there is a single present tense in Arabic, as compared to English, which has the simple and continuous forms. These differences result in errors such as She good teacher, When you come to Germany?, I flying to Egypt tomorrow or Where he going?
Arabic does not make the distinction between actions completed in the past with and without a connection to the present. This leads to failure to use the present perfect tense, as in I finished my work. Can you check it?
There are no modal verbs in Arabic. This, for example, leads to: From the possible that I am late. (I may be late.) Another common mistake is to infer that an auxiliary is needed and make mistakes such as: Do I must do that?
Grammar - Other: The indefinite article does not exist in Arabic, leading to its omission when English requires it. There is a definite article but its use is not identical with the use of the definite article in English. In particular, Arab learners have problems with genitive constructions such as the boy's dog. In Arabic this would be expressed as Dog the boy, which is how such constructions may be conveyed into English.
Adjectives in Arabic follow the noun they qualify. This leads Arab beginners to making word order mistakes in written or spoken English.
Arabic requires the inclusion of the pronoun in relative clauses, unlike English, in which the pronoun is omitted. This results in mistakes like: Where is the pen which I gave it to you yesterday?
Vocabulary: There are very few English/Arabic cognates. This significantly increases a.) the difficulties they have in comprehending what they hear and read, and b.) the effort they must make to acquire a strong English word store.