As a verb smog

is (smyga).

As a noun pollution is

the act of polluting or the state of being polluted, especially the contamination of the environment by harmful substances.

As nouns the difference between routine and variety

is that routine is a course of action to be followed regularly; a standard procedure while variety is the quality of being varied; diversity.

As an adjective routine

is according to established procedure.

As nouns the difference between reversion and retrogression

is that reversion is reversion while retrogression is retrogression (decline).

As a noun oxygen

is a chemical element (symbol o) with an atomic number of 8 and relative atomic mass of 159994.

As a proper noun death is

the personification of death, often a skeleton with a scythe, and one of the four horsemen of the apocalypse.

As a verb strolling is

.

As a noun strolling is

the taking of a stroll.

As a symbol pt is

.

As nouns the difference between estimation and classification

is that estimation is the process of making an estimate while classification is the act of forming into a class or classes; a distribution into groups, as classes, orders, families, etc., according to some common relations or attributes.

As verbs the difference between abrupt and erupt

is that abrupt is to tear off or asunder while erupt is to violently eject.

As an adjective abrupt

is broken away (from restraint).

As a noun abrupt

is something which is abrupt; an abyss.

As nouns the difference between clustering and association

is that clustering is the action of the verb to cluster while association is the act of associating.

As a verb clustering

is present participle of lang=en.

Fosfate is likely misspelled.

Fosfate has no English definition.

As a noun phosphate

is any salt or ester of phosphoric acid.

As a verb phosphate

is to treat or coat with a phosphate or with phosphoric acid.