Articulation therapy “Articulation” errors are widely known as lisps. American Speech and Hearing Association defines it like this:
“An articulation disorder is the atypical production of speech sounds characterized by substitutions, omissions, additions or distortions that may interfere with intelligibility.”
ASHA has a nice chart showing a when specific sounds are expected to develop. The link:
https://www.asha.org/siteassets/practice-portal/latelanguage-emergence/consonant-acquisitionchart.pdf
Whatever the causes, the ultimate goal is to help a person (of any age) to learn how to make the speech sound so that it no longer sounds “funny.” Please ask me for a free consultation if you or your child has a speech sound (or more) that needs attention.