Present continuous and present perfect continuous

Incorrect: I am working for the last two hours.

Correct: I have been working for the last two hours.

An abbreviation is a word or phrase written out in a brief way using only the letters of the alphabet and possibly full stops. In modern British English, abbreviations are written without full stops. Full stops (periods) are common in American English.

A pronoun is a word used instead of a noun. There are very many kinds of pronouns.

Personal pronouns

Read the following sentences:

Adverbs are words like carefully, slowly, happily, here, tomorrow and soon. An adverb usually qualifies a verb or a verb phrase and tells more about the manner, time, place or circumstances of the action or state denoted by the verb or verb phrase.

An adjective is a word like big, beautiful, sad, happy, interesting and sudden. An adjective qualifies a noun and denotes a temporary or permanent quality associated with it. For example, a beautiful woman is a woman who is distinguished from other women by being beautiful. Here the adjective beautiful denotes a permanent quality associated with the noun woman.
Similarly, a sad woman is a woman distinguished from other women by being sad. Here the adjective sad denotes a temporary quality associated with the noun woman.
Some adjectives are different: they do not denote a quality of the noun. For example, the adjective heavy as used in heavy smoker does not denote a quality of the noun smoker. It just shows a habit of the smoker.