I couldn't articulate "th" until I was 14. In some words, I used to pronounce it "n", as in "what is nat?" and in other words as "f" ("I fink nat..."). I switched to "d" so I was saying "what is dat?" which was better and it eventually led to me being able to pronounce it.
My local dialect renders certain "th"s as "f" as standard though so I still pronounce some that way.
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~Zinc Alloy aka. Russell~
WP's most sparkling member.
DX classic autism 1995, AS 2003, depression 2008
~INFP~