Quick Answer

When the “th” sound becomes a “d” sound , linguists call this phonological process th-stopping (or TH-stopping). It’s a type of sound substitution where the fricative “th” (/ð/ or /θ/) is replaced by a stop consonant like “d” or “t”.

What Is Th-Stopping?

Th-stopping happens when speakers replace the dental fricative “th” with a stop consonant that’s easier to articulate in certain contexts or dialects.

  • Voiced “th” (/ð/) → often becomes “d” (e.g., this → dis , they → day)
  • Voiceless “th” (/θ/) → often becomes “t” (e.g., think → tink , bath → bat)

This is considered a phonological process , which is a normal pattern in both child language development and many adult dialects.

Where Do You Hear This?

Th-stopping shows up in several English-speaking contexts:

  • Regional dialects : Common in parts of London (Cockney, Multicultural London English), Liverpool, some U.S. Southern and African American Vernacular English (AAVE) communities.
  • Child speech : Many children naturally use th-stopping while learning to talk; it usually resolves with age.
  • Informal speech : Some speakers use it casually or stylistically, even if they can produce standard “th” in formal settings.

How It Differs from T-to-D Flapping

Don’t confuse th-stopping with t-flapping , another common sound change in American English where “t” between vowels sounds like a quick “d” (e.g., better → bedder , water → wader). Th-stopping specifically involves the “th” digraph , not the letter “t”.

In a Nutshell

  • Term : Th-stopping (or TH-stopping)
  • Process : Substitution of “th” fricatives with stop consonants (“d” or “t”)
  • Contexts : Dialects, child speech development, informal registers

“That” becomes “dat,” “there” becomes “der” — classic examples of th- stopping you’ll hear in everyday London speech and other dialects.

Information gathered from public forums or data available on the internet and portrayed here.