what does the word [n] mean in math

Hello!

For real number
`x,` the symbol `[x]` means the integer part of `x,` i.e. the largest integer number not greater
than `x.`

In decimal notation for positive `x=n.mkl...,`

`[x]=n.`

For example, `[2.1]=2.`

 

For negative `x=-n.mkl...`

`[x]=-n-1` if some numbers `m, k, l, ...`
aren't zero.

For example, `[-2.1]=-3.`

 

For any integer `x`    `[x]=x.`

 

Sometimes this function is called floor function and is
denoted `|__x__|.`

The ceiling function is defined as
the smallest integer not less than `x` and is denoted `|~x~|.`