---
tag: 5JSWM1HBX2
kind: concept
name: Wedge sum
msc: [54B17, 55P99]
sources:
  - url: https://en.wikipedia.org/wiki/Wedge_sum
same_as:
  wikidata: Q1781358
  wikipedia: Wedge sum
---

## Summary

The wedge sum of a family of [[pointed spaces|T9DG8DDE75]] is their disjoint union with all base points glued to one point.
It is the coproduct in the category of pointed spaces.
Wedges of circles and of spheres are the basic building blocks of CW complexes and appear throughout homotopy theory.

## Explanations

### L1 human

Take several spaces, each with a marked point, and glue them together at the marked points only.
The result looks like a bouquet of flowers tied at one spot.
For example, the wedge of two circles is the figure eight.
Its fundamental group is the free group on two generators.