# `not`

_Not zero_
```syntax
not x    not[x]
```

Returns `1b` where `x` is equal to zero, and `0b` otherwise.

`not` applies to all datatypes except symbol and GUID, and to items of lists, dictionary values, and table columns. It tests the underlying data value.

Nulls and infinities never equal zero.
```q
q)not -1 0 1 2
0100b

q)not "abc","c"$0
0001b

q)not `a`b!(-1 0 2;"abc","c"$0)
a| 010b
b| 0001b

q)not 2000.01.01 2020.06.30
10b

q)not 00:00:00
1b

q)not 12:00:00.000000000
0b

q)not (0W;-0w;0N)
000b
```

`not` is an atomic function.

`not` is a [multithreaded primitive](mt-primitives.md).

---

[`neg`](neg.md)


[Logic](by-topic.md#logic)


_Q for Mortals_
[§4.3.2 Not Zero `not`](../learn/q4m/4_Operators.md#432-not-not)