It can be both depending on where it is used.
The noun 'youth' is an uncountable noun a word for a period in one's life.The noun 'youth' is a count noun as word for a young person. The plural is youths.
The plural form for the noun youth is youths. The plural possessive form is youths'.Example: There is a calendar of youths' activities posted on the bulletin board.
practitioner is singular (plural practitioners)sofa is singular (plural sofas)satellite is singular (plural satellites)clips is plural (singular clip)dentist is singular (plural dentists)dollars is plural (singular dollar)article is singular (plural articles)magazines is plural (singular magazine)laminator is singular (laminators is plural)radios is plural (singular radio)
singular and plural
Singular: book / Plural: books Singular: cat / Plural: cats Singular: child / Plural: children Singular: foot / Plural: feet
Are is plural. "Is" is singular. For example, "There is a glove on the chair". That is singular. "There are gloves on the chair". That is plural.
"Has" is singular, e.g. He has, she has. "Have" is plural, e.g. They have, we have. The exception is "I" - e.g. I have.
The word team is singular; the plural form is teams.
Who may be singular or plural.
This is singular. These is the plural form.
These is plural, this is singular
'These' is the plural form of 'this'.