Montessori glossary

Eight words that turn up in every Montessori album, each defined in its first sentence, tied to a lesson that shows it, and sourced to Montessori's own books from 1912 to 1917 by passage.

If you read only one, read control of error, then present the knobbed cylinders, where it is easiest to see.

Control of error

Control of error is the feature built into a Montessori material that shows the child a mistake without an adult saying anything: a cylinder with no hole left to go in, a step that breaks the line of a stair.

Three-period lesson

The three-period lesson is how a Montessori adult teaches a name in three short steps: say the name, ask the child to pick out the thing named, then ask the child to say the name.

Normalization

Normalization is Montessori's later word for the calm, settled state she saw in children after long stretches of concentration on work they chose themselves.

A later term; the page cites the earlier passages behind it.

Sensitive periods

A sensitive period is a stretch of early childhood when a child takes in one kind of learning, such as the sounds of speech, with an ease that later ages do not have.

A later term; the page cites the earlier passages behind it.

Planes of development

The planes of development are Montessori's division of growing up into four stages, the first three running from birth to 6, 6 to 12 and 12 to 18, each with its own way of learning.

A later term; the page cites the earlier passages behind it.

Work cycle

The work cycle is the long, unbroken block of time, usually a morning, in which a Montessori child chooses work, settles into it and finishes on their own.

Isolation of difficulty

Isolation of difficulty means building a material or a lesson so the child meets one new difficulty at a time, with everything else held the same.

Prepared environment

The prepared environment is the room, furniture and shelf of materials an adult sets up so a child can choose work, reach it, use it and put it back without help.

Some of these names never appear in the 1912 to 1917 books; normalization and planes of development come from her later books, which are still in copyright. Each page says when that is the case and cites the earlier passages that describe the idea. Nothing is quoted from a book we have not checked.