As initialisms the difference between if and ik

is that if is interactive fiction while ik is (text messaging) i know.

As a noun geodes

is .

As a proper noun jewels is

.

As nouns the difference between fascia and valance

is that fascia is a wide band of material covering the ends of roof rafters, sometimes supporting a gutter in steep-slope roofing, but typically it is a border or trim in low-slope roofing while valance is short curtain that hangs along the top edge of a window.

As nouns the difference between academic and specialist

is that academic is while specialist is someone who is an expert in, or devoted to, some specific branch of study or research.

As adjectives the difference between academic and specialist

is that academic is while specialist is (british) specialised.

As nouns the difference between egghead and specialist

is that egghead is (pejorative) a bald person, especially a man while specialist is someone who is an expert in, or devoted to, some specific branch of study or research.

As an adjective specialist is

(british) specialised.

As an adjective injurious

is causing physical harm or injury; harmful.

As a verb injuring is

present participle of injure.

As verbs the difference between appended and postfixed

is that appended is past tense of append while postfixed is past tense of postfix.

As an adjective postfixed is

subjected to postfixation.

As an adjective available

is such as one may avail one’s self of; capable of being used for the accomplishment of a purpose.

As a verb availed is

(avail).

As adjectives the difference between subversive and riotous

is that subversive is intending to subvert, overturn or undermine a government or authority while riotous is having the characteristics of a riot.

As a noun subversive

is a radical supporter of political or social revolution.

As an adjective subversive

is intending to subvert, overturn or undermine a government or authority.

As a noun subversive

is a radical supporter of political or social revolution.

As a proper noun underground is

(uk|rail transport) the london underground.