As an educational device, "one word substitutes" are essentially words that correspond to definitions instead of vice versa.
Examples would include:
Having no clear meaning - vague, ambiguous
Not able to be halted - unstoppable
Able to be changed - changeable, mutable
Occurring on and off - intermittent, transient
The term is used by various English education sites to mean a word that fits a certain definition. This is similar to finding the words in a crossword puzzle from the clue.
The word is newcomer.
The word could be healthy for being free from infection.
A+ Students: euphemism
Substitution
Euphemisms are more sensitive word substitutions.
examples of one syllable words
In basketball, a substitution is when one player goes in for another.
Font substitution is when one font is used in place of another. This is typically done when the original font is unavailable or does not contain glyphs for the required characters. Adobe Reader, Microsoft Word, OpenOffice, and most recent browsers are capable of performing font substitution.
An ablaut is the substitution of one root vowel for another in a word, to reflect grammatical information, such as "get, gat, got".
There is not Substitution Property of Congruence. There is, however, one for Equality, called the Substitution Property of Equality.
frameshift mutation
It means that you substitute one expression by another, as a step of the integration. When you do a substitution, you must not forget to also substitute the differential in the integral, for example the "dx" (if the variable integrated is "x"). You can find some examples on how to do this in the Wikipedia article on "integration by substitution".