SSC CHSL · Bite-size lessons

Classification

About 7 min · General Intelligence and Reasoning · English

Time worked out from the lesson's 454 words at 150 words a minute, plus a minute for each question.

Classification is a pattern-recognition topic in the SSC CHSL Reasoning section where you identify the odd one out from a group of four or five items. These items may be words, numbers, letters or figures. The examiner tests your ability to spot a common property shared by all but one element.

Key ideas

• Odd One Out principle: Three or four items share a common property; one does not. Your task is to identify the exception, not to find a difference between any two items.
• Number classification: Properties include odd/even, prime/composite, perfect square/cube, multiples of a number, divisibility rules, digit sum patterns and arithmetic sequences.
• Letter classification: Check vowel/consonant status, positional value in alphabet (A=1, Z=26), number of letters in a word, or alphabetical patterns like every alternate letter.
• Word classification: Semantic grouping — all are capitals except one, all are rivers except one, all are metals except one. Requires general awareness of categories like Indian states, currencies, scientists, inventions, sports terms.
• Figure classification: Visual properties — symmetry (horizontal, vertical, both or none), number of sides, open/closed shapes, shading patterns, rotation angles, number of elements inside a figure.

Watch out for

• Picking the first difference noticed without checking all items → Always verify that exactly three items share a property and only one does not. Sometimes two properties overlap; choose the more fundamental one or the one that isolates exactly one item.
• Confusing "odd one out" with "different from one other" → The odd item must differ from all the rest on the same criterion, not just from one neighbour. If two items differ from the other three, re-examine your property.
• Ignoring general knowledge in word classification → If the question says "Copper, Iron, Mercury, Aluminium," many students miss that Mercury is a liquid metal, or that it's toxic, depending on context. Brush up on basic categories in science, geography and polity.

Quick reference

• Process: Identify the common property of three items; the fourth that lacks it is the odd one.
• Number checks: Prime/composite, odd/even, perfect square/cube, divisibility, digit sum.
• Letter checks: Vowel/consonant, alphabetical position (odd/even), word length.
• Word checks: Semantic category (capitals, rivers, metals, scientists); requires general awareness.
• Figure checks: Symmetry type, number of sides, open/closed, shading, element count.

Check yourself: 3 questions

This lesson is cut from the topic's note, not rewritten. Fact-checked on 18 Oct 2026: an AI-assisted check of this note against cited sources; the errors it found were corrected that day. Some errors may remain. The questions are from Shishya's validated question bank.

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