advisable
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advisable
Describes an action or decision that is smart, sensible, and recommended because it is likely to lead to a good outcome.
Angesichts des angekündigten Sturms ist es nicht ratsam, eine Bergwanderung zu unternehmen.
In view of the announced storm, it is not advisable to go on a mountain hike.
The adjective 'ratsam' (advisable) is derived directly from the noun 'der Rat' (advice). The ending '-sam' means something like 'full of' or 'having the quality of'. So something is 'ratsam' if it has the quality of good advice.
Wenn dir jemand einen guten Rat gibt, ist seine Empfehlung ratsam.
If someone gives you good advice, their recommendation is advisable.
'Ratsam' (advisable) is almost always used in the impersonal construction 'Es ist ratsam, ... zu + infinitive' (It is advisable to ...). This structure is very typical for expressing a recommendation.
Es ist ratsam, vor einer Prüfung gut zu schlafen.
It is advisable to sleep well before an exam.
The word 'ratsam' (advisable) belongs more to a formal style of language. You often find it in written recommendations, official notices, or in carefully considered spoken language.
In der Bedienungsanleitung steht, es sei ratsam, das Gerät regelmäßig zu reinigen.
The instruction manual says it is advisable to clean the device regularly.
necessary
'notwendig' and 'ratsam' both have to do with a suitable action in a situation. The difference lies in strength. 'notwendig' means that something is really needed or absolutely must happen. Without that thing, it does not work properly. 'ratsam' means that something is wise and advisable, but not necessarily required or absolutely necessary. The words can be confused because both often appear in advice. Remember: 'notwendig' is stronger than 'ratsam'.
Bei diesem Wetter ist es ratsam, eine Regenjacke mitzunehmen.
In this weather, it is advisable to take a rain jacket with you.
Für die Anmeldung ist ein gültiger Ausweis notwendig.
A valid ID is necessary for registration.