Imaginable or conceivable. The word is almost always used for emphasis, often in the form 'alle erdenklichen...' (all conceivable...) or in superlatives, to express that all possibilities are included.
example
Wir haben alle erdenklichen Vorkehrungen getroffen, um das Fest sicher zu machen.
We have taken every conceivable precaution to make the festival safe.
Usage tips
Word structure
The adjective is derived from 'denken' (to think). The prefix 'er-' often indicates that a state is reached, and the ending '-lich' forms the adjective. Literally, it therefore means 'reachable through thinking' or 'conceivable'.
EXAMPLE
Es gibt viele erdenkliche Gründe für sein Verhalten.
There are many conceivable reasons for his behavior.
Emphasis with 'alle'
'Erdenklich' (conceivable) is very often used together with 'alle' (all) to express that truly every possibility is meant. The form is then always 'alle erdenklichen' + plural noun.
EXAMPLE
Das Geschäft bietet Schokolade in allen erdenklichen Geschmacksrichtungen an.
The store offers chocolate in every conceivable flavor.
Emphasis with superlative
Another typical use is the combination with a superlative. It emphasizes that something is the absolute best, worst, or greatest that one can imagine.
EXAMPLE
Das war die beste erdenkliche Lösung für das Problem.
That was the best conceivable solution to the problem.
Compare with
near_synonym · confusable
erdenklich vs möglich
possible
'möglich' and 'erdenklich' both have to do with what one can imagine. 'möglich' is neutral and very common: it can mean that something may happen or is conceivable. 'erdenklich' sounds stronger and is mostly used in fixed expressions like 'alle erdenklichen' (all conceivable). This means: truly everything one can imagine. Learners may confuse the words because both are about possibilities. In normal sentences, you usually say 'möglich'; 'erdenklich' is more suitable for emphasis.
erdenklich
Die Firma bietet alle erdenklichen Hilfen für neue Mitarbeiter an.
The company offers every conceivable kind of support for new employees.
möglich
Es ist möglich, dass der Zug heute später kommt.
It is possible that the train will arrive later today.