The word 'physics' is a noun, a word for the science or study of nature and properties of matter and energy; a word for a concept; a word for a thing.
Physics is naturally part of the natural sciences. Physics deals originally dealt with the movement of things and how things worked. Physics in the modern world has grown to be a lot more advanced.
"Wavelength" is a noun.
An adjective
"Sunshine" is a noun.
Dew is a noun.
It can be an adjective if the sentence is something like "We faced physical challenges today." It can also be a noun if you're saying "I'm going to the doctor for my physical."
Speech sounds are specific sounds. The word physics would be pronounced as: fis - ics or fiz - ics
Thermodynamics is part of physics.
part of speech
The part of speech for this particular word is a noun.
The part of speech for "answer" is a noun.
adverb
what part of speech is beneath
The part of speech for "explicit" is an adjective.
The part of speech for "twirl" is a verb.
The part of speech for "unfamiliar" is an adjective.
The part of speech of "came" is a verb.