Adjectives in Bengali, similar to their English counterparts, do not inflect for gender or case. Additionally, they do not inflect for number either! This means that once you know an adjective, you can apply it to any noun(s) without any consideration.
To take an example, consider the adjective 'tall'; the Bengali word for it is লম্বা ("lambaa"). Observe how the adjective (in bold letters) remains the same in the example below:
|the tall boy||লম্বা ছেলেটা|
|the tall girl||লম্বা মেয়েটা|
|the tall boys||লম্বা ছেলেরা|
|the tall girls||লম্বা মেয়েরা|
Notice how only the definite markers (indicating singular/plural noun) change in the example above. Keep in mind, however, that since the definite markers can be omitted, লম্বা ছেলে can mean "tall boy" or "tall boys"; you will have to use the context to determine which one makes sense.
We have already seen how demonstrative pronouns (see chapter on pronouns for details) function in Bengali. Demonstrative adjectives follow exactly the same pattern with only one difference: the definite article is attached to the noun instead of the adjective. Let's look at some examples:
|This is mine||এটা আমার|
|This book is mine||এই বইটা আমার|
|That is mine||ওটা আমার|
|That book is mine.||ওই বইটা আমার|
So while the pronouns 'this' and 'that' translated to এটা and ওটা, the demonstrative adjectives translate to এই and ওই, with the definite singular/plural markers attached to the noun following these adjectives. So "this book" is এই বইটা, "these books" is এই বইগুলো; "this boy" is এই ছেলে, and "these boys" is এই ছেলেরা.