"is threading" is the present progressive tense of the verb thread.
Multi-threading is not part of the language.
You feed the aglet on the lace through the eyelet on the shoe.
One part is the HEAD, another is the THREADING and i would guess the other is called the shaft (not sure about that)
The part of speech for this particular word is a noun.
part of speech
The standard threading size for bike pedal threading is 9/16 inch.
The part of speech for "answer" is a noun.
what part of speech is beneath
adverb
The part of speech for "explicit" is an adjective.
The part of speech for "lecturer" is a noun.
The part of speech for "rapid" is an adjective.