In the following question, out of the four alternatives, select the word that is similar in meaning to the given word Monotonous.

Introduction / Context:
This is a vocabulary question that asks you to find a synonym, or word with similar meaning, for the adjective monotonous. This word is often used in descriptions of work, speech, music or daily routines. To answer correctly, you need to recall what monotonous means and then match it with the option that best captures that sense.

Given Data / Assumptions:
- Target word: Monotonous. - Options: Dull, Timid, Unfriendly, Lusty. - Only one option should reflect the core meaning of monotonous in common usage.

Concept / Approach:
Monotonous refers to something that is repetitive, lacking variety and therefore boring or tiresome to experience. For example, a monotonous job or a monotonous lecture does not change much and quickly becomes dull. The synonym we choose should therefore convey the idea of boredom, lack of variety or uninteresting quality. Words related to fear, social behaviour or energy levels will not match this meaning.

Step-by-Step Solution:
Step 1: Define monotonous as repetitive and lacking variety, so that it becomes boring or tedious. Step 2: Examine Dull. Dull can mean boring, not exciting, and lacking interest or brightness. This matches the sense of monotonous closely. Step 3: Examine Timid. Timid means shy or lacking courage. It describes personality or behaviour, not the repetitive quality of an activity. Step 4: Examine Unfriendly. Unfriendly refers to a cold or hostile attitude, again unrelated to repetition or boredom. Step 5: Examine Lusty. Lusty means strong, healthy and full of energy, which is almost the opposite of dullness.

Verification / Alternative check:
Use the word in a typical context. A monotonous lecture can be described as a dull lecture, and the meaning remains almost the same. However, calling it a timid lecture, unfriendly lecture or lusty lecture would change the meaning completely and would not sound natural. Similarly, a monotonous routine is a dull routine, not a timid or unfriendly routine. This context based check confirms that dull is the closest synonym among the options.

Why Other Options Are Wrong:
Timid is wrong because it focuses on fear and shyness, not on boredom or repetition. Unfriendly is wrong because it refers to a lack of warmth in social relations, not to a lack of variety. Lusty is wrong because it suggests energy and vigour, which is quite different from the flat and boring sense of monotonous.

Common Pitfalls:
Some students may confuse monotonous with words that sound similar but are different in meaning, such as monotheist or monotone. It helps to remember typical phrases like monotonous routine, monotonous work and monotonous voice. In all these cases, you can safely replace monotonous with dull, boring or repetitive. Building such mental associations between words and common contexts is extremely useful for answering synonym questions in competitive exams.

Final Answer:
The word that is similar in meaning to Monotonous is Dull.