substitution

Everyday

1. A substitution is putting one person or thing in the place of another. tree →
2. (sport) A substitution is when a player is taken off and another player comes on. tree →
3. (maths) Substitution means replacing a letter in an expression or formula with a number, to work out its value. tree →
4. (cooking) A substitution is using a different ingredient instead of the one in the recipe. tree →

In the lessons

In maths lessons substitution is a key algebra skill: «If a = 3, find 2a + 1» — you substitute 3 for a to get 7. In science, a substitution reaction swaps atoms. In sport it is changing players. In codes, a substitution cipher swaps letters for other letters. Phrases: make a substitution, by substitution, substitution cipher.

Examples

• The coach made a substitution at half-time. tree →
• By substitution, if x = 4, then 3x = 12. tree →
• Use substitution to check your answer to the equation. tree →
• We used honey as a substitution for sugar. tree →
• In a substitution cipher, A might become D and B might become E. tree →
• Two substitutions changed the whole match. tree →
• Substitution of the ingredients made the cake taste different. tree →

Note

Verb substitute: you substitute the new thing FOR the old one (substitute 5 for x). In maths, put brackets when substituting negatives: if a = −2, a² = (−2)² = 4. Countable for single changes (two substitutions).

In Jewish tradition

Interpretation: Sefer Yetzirah and later Kabbalists used systems of swapping Hebrew letters for other letters according to fixed schemes to find hidden meanings. In the primary lessons: In maths lessons substitution is a key algebra skill: «If a = 3, find 2a + 1» — you substitute 3 for a to get 7. In science, a substitution reaction swaps atoms. In sport it is changing players. In codes, a substitution cipher swaps letters for other letters. Phrases: make a substitution, by substitution, substitution cipher.

Examples

• The Kabalistic principles involved in the reversal of Hebrew letters, and their substitution by others, on definite schemes, should also be studied and borne in mind. (Sefer Yetzirah, Westcott 1893) tree →

Note

Verb substitute: you substitute the new thing FOR the old one (substitute 5 for x). In maths, put brackets when substituting negatives: if a = −2, a² = (−2)² = 4. Countable for single changes (two substitutions).