Are poplin and broadcloth the same fabric?

In contemporary shirting, functionally yes. Both name a smooth, tightly woven plain-weave cotton. The words carry different histories, ribbed papeline from Avignon and fulled English wool, but the cloths on a modern shirt rack are interchangeable.

Why is wool broadcloth so different from shirt broadcloth?

Because the original broadcloth was defined by its finishing, not its fiber. The wool was woven extra wide and then fulled, shrunk and felted until the weave disappeared. Only the name migrated to cotton shirting.

Side by side

Poplin vs Broadcloth

In modern shirting, poplin and broadcloth are nearly the same cloth: a fine, tightly woven plain-weave cotton with a smooth face. The distinction is mostly historical and regional. Poplin descends from a ribbed cloth with a heavier weft, and the name broadcloth descends from the great fulled wool of medieval England before American mills borrowed it for fine shirting.

Poplin

No. 029

plain weave, fine crosswise rib · first documented 1400s

Broadcloth

No. 030

plain weave (historically fulled wool) · first documented 1300s

The differences

Aspect	Poplin	Broadcloth
Today	Fine plain-weave shirting; the name dominant in British usage.	Effectively the same shirting; the name dominant in American usage.
Historically	Silk warp with a heavier wool weft, giving a fine crosswise rib.	Wool woven oversize on a broad loom, then fulled into a dense, felted cloth.
Rib	May keep a barely visible crosswise rib when the weft is heavier.	None; the modern cotton is smooth and even.
Hand	Crisp, cool, dressy; creases sharply.	Marginally softer in many commercial versions; otherwise identical.

Which to choose

For a modern dress shirt, treat the two names as one cloth and judge the fabric in hand instead: yarn fineness and thread count matter far more than which word is on the label. If a swatch shows a distinct crosswise rib, it is leaning into the older sense of poplin.

Common questions

Are poplin and broadcloth the same fabric?: In contemporary shirting, functionally yes. Both name a smooth, tightly woven plain-weave cotton. The words carry different histories, ribbed papeline from Avignon and fulled English wool, but the cloths on a modern shirt rack are interchangeable.
Why is wool broadcloth so different from shirt broadcloth?: Because the original broadcloth was defined by its finishing, not its fiber. The wool was woven extra wide and then fulled, shrunk and felted until the weave disappeared. Only the name migrated to cotton shirting.

Full entry: Poplin Full entry: Broadcloth

Sources & References

1.Poplin, Wikipedia
2.poplin, Online Etymology Dictionary
3.Broadcloth, Wikipedia
4.broadcloth, Online Etymology Dictionary