In English vocabulary, which word is used for a thing that is no longer in use and has become outdated or out of fashion?

Introduction / Context:
This is a classic one word substitution question from English vocabulary. The examiner gives a short definition a thing no longer in use and asks you to choose the single word that best matches this idea. Such questions are very common in competitive exams because they test both your vocabulary range and your ability to distinguish between similar looking but different words.

Given Data / Assumptions:

• The phrase given in the stem is a thing no longer in use.
• We need a word that describes objects, ideas, or practices that are no longer used because they are outdated or have been replaced.
• Option A: Illusion.
• Option B: Illegal.
• Option C: Obsolete.
• Option D: Historic.
• We assume standard modern English dictionary meanings for all options.

Concept / Approach:
The key word in the definition is no longer in use. When an object, a practice, or a technology has been replaced by something newer and is not used any more, we describe it as obsolete. For example, floppy disks are now obsolete. Illusion means something that deceives the senses or a false impression. Illegal means against the law. Historic means important in history or old in a positive sense. Only obsolete directly captures the idea that something has fallen out of use due to age or progress.

Step-by-Step Solution:
Step 1: Focus on the idea no longer in use and connect it with real life examples such as old machines or outdated customs.Step 2: Recall that obsolete is typically used for old technologies, rules, or ideas that people do not use any more.Step 3: Check illusion; it refers to something that appears real but is not, such as a magic trick or optical effect, and is unrelated to being out of use.Step 4: Check illegal; this describes something that breaks a law, not something that has simply become outdated.Step 5: Check historic; this word emphasises historical importance, not the fact that a thing has stopped being used. Therefore, obsolete is the only word that exactly fits the definition.

Verification / Alternative check:
Try using each option in a test sentence. A typewriter is now ______. If we insert obsolete, the sentence becomes A typewriter is now obsolete, which sounds natural and correct. If we use illusion, illegal, or historic, the meaning changes completely and no longer matches the idea that people do not use typewriters any more. This quick substitution test confirms that obsolete is the intended answer for a thing no longer in use.

Why Other Options Are Wrong:
Illusion is connected with deception and false appearances, not with being outdated. Illegal means not permitted by law and is used for actions or items banned by legal rules, such as illegal drugs. Historic describes something that is famous or important in history, like a historic building or a historic event, and does not necessarily mean that it is no longer used. None of these alternatives expresses the specific concept given in the stem.

Common Pitfalls:
Some learners assume that any word related to the past, such as historic, might match no longer in use, but that is not always true. Historic often has a positive tone and focuses on importance, whereas obsolete is neutral or negative and focuses on the fact that something has been replaced and discarded. Remembering that obsolete goes with old technology and rules, while historic goes with important events and monuments, will help you avoid confusion in exam situations.

Final Answer:
The correct one word substitution for a thing no longer in use is Obsolete, so option C is correct.