ADJ by n
The 'available' group
These adjectives indicate that something can be done. The noun group following the preposition by indicates how it can be done. Most of the adjectives in this group are related to verbs. For example, if an illness is curable, this means you can cure it. However, we include here available which is not related to a verb but which indicates that something can be obtained.
They include activation codes that are only available by phone or over the internet.
Acts of violence will always be explainable by arguments about urban deprivation, poverty and educational underachievement.
In the case of achievable, attainable, available, and obtainable, the preposition by is sometimes followed by an '-ing' clause.
achievable attainable available curable explainable explicable obtainable preventable treatable
Victory would be only achievable by reducing the city to rubble.