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# Segments

> Subsets of contacts in an audience, defined by their attributes, activity, or tags.

## The basics

A segment is a named subset of the contacts in an audience. Mailchimp
distinguishes three kinds of segment:

| Type           | What it is                                                                                                                                                                                                                                        |
| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Saved segment  | You define conditions—signup date, campaign engagement, merge field values, e-commerce activity, and more—and its membership is every contact who currently matches them. Membership isn't fixed; it's recalculated as your contact data changes. |
| Static segment | You add contacts to it explicitly, with no conditions. Membership only changes when you add or remove someone.                                                                                                                                    |
| Fuzzy segment  | A Mailchimp-generated segment, such as a "similar subscribers" segment.                                                                                                                                                                           |

**Static segments are also tags.** When you [tag a contact](/marketing/concepts/audiences/contacts#tags), Mailchimp creates or reuses a static segment behind the scenes. A static segment and a tag are the same underlying object, just reached through different features. See [Contacts](/marketing/concepts/audiences/contacts#tags) for tagging.

## Segment conditions

A saved segment's conditions are grouped under a match type, `any` or `all`,
which determines whether a contact needs to satisfy just one condition or
every condition to belong to the segment. Each condition targets a specific
kind of data—a merge field, a campaign interaction, a purchase, a location—and
each kind of data has its own condition shape, documented in
[Alternative schemas](/marketing/api-concepts/alternative-schemas).

> **Note**
>
> The Marketing API supports regular segments only: a single match type applied
> across up to 10 conditions. The Mailchimp app also offers the advanced segment
> builder, which nests and/or logic across groups of conditions with no limit on
> count. Advanced segments aren't available through the API yet.

## Working with segments through the API

The [Segments endpoints](/marketing/api/lists/list-segments) let you create,
update, and delete segments, and read back which contacts currently belong to
one with [List members in segment](/marketing/api/lists/list-segment-members).
For a saved segment, that membership list reflects the conditions evaluated
against your contacts right now, not a snapshot from when the segment was
created.