As nouns the difference between fermion and antifermion

is that fermion is a particle with totally antisymmetric composite quantum states, which means it must obey the Pauli exclusion principle and hence Fermi–Dirac statistics. They have half-integer spin. Among them are many elementary particles, most derived from quarks. Compare boson while antifermion is the antiparticle of a (specified) fermion.

As a noun wavelength

is the length of a single cycle of a wave, as measured by the distance between one peak or trough of a wave and the next; it is often designated in physics as λ, and corresponds to the velocity of the wave divided by its frequency.

As an adjective extraspectral is

producible by a combination of wavelengths but not by any single wavelength.

As nouns the difference between aversion and xanthophobia

is that aversion is aversion while xanthophobia is (rare) an aversion to yellow light.

As nouns the difference between yellow and xanthophobia

is that yellow is (yellow) the colour of gold or butter; the colour obtained by mixing green and red light, or by subtracting blue from white light while xanthophobia is (rare) an aversion to yellow light.

As an adjective yellow

is having yellow as its colour.

As a verb yellow

is to become yellow or more yellow.

As adjectives the difference between class and crossclass

is that class is (irish|british|slang) great; fabulous while crossclass is spanning several classes or categories.

As a noun class

is (countable) a group, collection, category or set sharing characteristics or attributes.

As a verb class

is to assign to a class; to classify.

As a noun language

is (lb) a body of words, and set of methods of combining them (called a grammar), understood by a community and used as a form of communication or language can be a languet, a flat plate in or below the flue pipe of an organ.

As a verb language

is to communicate by language; to express in language.

As an adjective crosslinguistic is

spanning several languages.

As an adjective antiviral

is (medicine) inhibiting the growth and reproduction of a virus.

As a noun ibacitabine is

a particular antiviral drug.

As nouns the difference between drug and ibacitabine

is that drug is (pharmacology) a substance used to treat an illness, relieve a symptom, or modify a chemical process in the body for a specific purpose or drug can be (obsolete) a drudge while ibacitabine is a particular antiviral drug.

As a verb drug

is to administer intoxicating drugs to, generally without the recipient's knowledge or consent or drug can be (drag).

As a noun astronomer

is one who studies astronomy, the stars or the physical universe; a scientist whose area of research is astronomy or astrophysics.

As an adjective copernican is

of or pertaining to (1473-1543), the influential astronomer.

As adjectives the difference between subtractive and nonsubtractive

is that subtractive is of or pertaining to subtraction while nonsubtractive is not subtractive.