Correct spelling, explanation: scalable is an adjective and also a derivative of the verb scale. We can form verbal adjectives by adding a suffix to a verb, which is a root. The -able ending is a common word-forming element of English adjectives, typically based on verbs. It comes from French -able and directly from Latin -abilis, meaning capable of. If the verb ends with a silent -e, we usually drop that vowel in a derivative. That’s why the only correct version is scalable, not scaleable.

Definition of scalable:
adjective, able to be scaled or climbed
The key point of this system is that it’s scalable.
My business needs a scalable, profitable strategy.

Collocations with scalable:
Some most commonly used collocations include: scalable technology and scalable font.
Scalable font can increase in size without causing any degradation in quality.
Scalable technology involves apps, platforms, or programs that can grow and adapt with ease.

Incorrect spelling, explanation: this mistake may come from the fact that the basic word of this adjective is scale. When we create a new verbal adjective, we add the suffix -able to the end of the root. The thing is that if a verb ends with a silent -e vowel, this letter must disappear in a derivative. That’s why the correct spelling is scalable, not scaleable.

Incorrect spelling

Incorrect spelling