Topic: Adjective (বিশেষণ),

Best Answer Explained in Below-:

In the provided question, we are asked to identify which word among the options is not an adjective. Adjectives are words that describe or modify nouns by providing additional information about them, such as their attributes, quantities, or qualities.

Let's analyze the options:

A) **Solar** - This word relates to the sun and describes something that derives energy or is derived from it, such as "solar energy." It functions as an adjective in contexts like "solar panels."

B) **Polar** - This term describes something related to the poles of the Earth, such as the climatic conditions in polar regions. Thus, it also serves an adjectival role in phrases like "polar bears."

C) **Linear** - This adjective describes something that is in a straight line or follows a clear sequence. It is often used in mathematics and other fields, such as "linear equations."

D) **Hammer** - This word, however, is a noun referring to a tool used for driving nails or breaking objects. It does not describe or modify another noun, which is the primary function of an adjective.

Thus, the correct answer is **D) hammer**, as it stands out as the only option that does not function as an adjective.