Indeclinable Word الْكَلْمَةُ الْمَبْنِيَّةُ

As learned in previous posts, the last letter (or huruf) of an Arabic word takes different vowel based on different cases, as follows:

1. nominative (or subjective) = dammah/dammatain, e.g كِتَابٌ
2. accusative (or objective) = fathah/fathatain, e.g كِتَابَ
3. genitive (or possessive) = kasrah/kasratain, e.g كِتَابٍ

Also, the vowel of the last huruf indicates that the word is either of the two shown below:

1. indefinite article, e.g كِتَابٌ
2. definite article, e.g الْكِتَابُ

There are, however, words that the vowels in their last huruf doesn't change no matter in what  context they are used. These type of words are called indeclinable word الْكَلِمَةُ الْمَبْنِيَّةُ. In short they are called مَبْنِى mabni. Here are examples of these type of words:

1. Interrogative article: مَاذَا what, مَنْ who, أَيْنَ where.
2. Determiners (or directing words): هَذَا this, ذَلِكَ that.
3. Preposition: فِي in, عَلَى up, إِلَى to.
4. Pronoun: هُوَ he, أَنْتَ you, نَحْنُ we.