How the adverb increasingly is possible?

[sky3120]

The gap is increasing.

The guy is running.

The baby is sleeping.

No one calls increasing and running and sleeping adjectives, but how increasingly can be an adverb and it is possible? but I have never seen runningly, sleepingly, etc. Is there a particular reason for the word, increasingly? Thank you so much as usual and have a good day.

[philo2009]

The gap is increasing.

The guy is running.

The baby is sleeping.

No one calls increasing and running and sleeping adjectives, but how increasingly can be an adverb and it is possible? but I have never seen runningly, sleepingly, etc. Is there a particular reason for the word, increasingly? Thank you so much as usual and have a good day.

Unfortunately, there is no absolutely reliable rule to predict the existence or non-existence of English words.

However, the adverb that you cite exists and is commonly used.

Is there anything else that you need to know?

[sky3120]

Thank you and you agree that increasing in the sentence functions as a verb, not an adjective, right? Thank you so much.

[philo2009]

Thank you and you agree that increasing in the sentence functions as a verb, not an adjective, right? Thank you so much.

'Increasing', e.g. in

An increasing number of people prefer Facebook to Twitter.

is a participle which, in common with all participles, is inherently capable of serving an adjectival function (here modifying 'number').

However, that alone is not necessarily sufficient for it to be classed as a true adjective by the lights of most modern grammarians.