As adjectives the difference between critical and eager

is that critical is inclined to find fault or criticize; fastidious; captious; censorious; exacting while eager is (obsolete) sharp; sour; acid.

As nouns the difference between critical and eager

is that critical is a critical value, factor, etc while eager is (tidal bore).

As adjectives the difference between substantial and number

is that substantial is having to substance; actually existing; real; as, substantial life while number is (numb).

As nouns the difference between substantial and number

is that substantial is anything having substance; an essential part while number is (countable) an abstract entity used to describe quantity.

As a verb number is

to label (items) with numbers; to assign numbers to (items).

As nouns the difference between fallback and setback

is that fallback is an act of falling back while setback is an obstacle, delay, or disadvantage.

As an adjective fallback

is that can be resorted to as a fallback.

As a preposition ajax

is (polari) nearby, over there.

As a noun social is

a festive gathering to foster introductions.

As an adjective social is

being extroverted or outgoing.

As a preposition ajax

is (polari) nearby, over there.

As a noun currency is

money or other items used to facilitate transactions.

As a preposition ajax

is (polari) nearby, over there.

As a noun country is

(label) an area of land; a district, region.

As an adjective country is

from or in the countryside or connected with it.

As a preposition ajax

is (polari) nearby, over there.

As a noun request is

act of (l).

As a verb request is

to express the need or desire for.

As nouns the difference between tracking and rest

is that tracking is the act by which something is tracked while rest is prison.

As a verb tracking

is .

As prepositions the difference between ajax and in

is that ajax is (polari) nearby, over there while in is in, into, within.

As nouns the difference between pair and column

is that pair is two similar or identical things taken together; often followed by of while column is a solid upright structure designed usually to support a larger structure above it, such as a roof or horizontal beam, but sometimes for decoration.

As a verb pair

is to group into sets of two.