Read the passage
A coral reef is a flower garden of stone, growing like a wall or like a tower from the depth and filled with the most confusing and most colorful varieties of life. The colors are beautiful, especially ins the shallow region down to sixty feet, where some of the red and yellow light of the sun's rays still penetrates. But most corals are greenish, brown, bluish or yellow. Coral reefs often shelter and food to thousands of creatures. The warn=mer the climate, the greater the variety of species there is. In the tropics. it is easier to find, in one place, ten different species than ten specimens of the same species and a coral reef provides ample proof of that rule. Living conditions are most favorable so that many forms are able to develop and survive in their struggle for existence.
যে word দ্বারা কোন কিছুর নাম প্রকাশ করা হয় তাকেই noun বলে । আম
যেমনঃ Man, Girl, Kamal, Badal, Rahim, Riya,, Dhaka, Bangladesh, Kolkata, Delhi.
Jhon Seely তাঁর Oxford A-Z of Grammar & Punctuation বইতে লেখেন,
Nouns are words used to identify people, places, things, and ideas.
Concrete Noun: যে Noun এর বাহ্যিক বা দৈহিক অবস্থিতি আছে এবং যাকে ইন্দ্রিয়ের দ্বারা উপলব্ধি করা যায় তাকে Concrete Noun বলে। যেমন: boy, book ইত্যাদি।
Noun কে প্রধানত পাঁচ ভাগে ভাগ করা হয়। যথা-