Learn Hardcore Turkish: Ölçüm doğru yapılmalı. - The measurement must be done correctly.

Ölçüm is a noun meaning “measurement.” It’s a deverbal noun (masdar) formed from the verb ölçmek (“to measure”) by removing the infinitive ending and adding -üm.

Why is yapılmalı used instead of yapmalı?

Because the sentence is in the passive voice: you want to say “the measurement should be done,” not “someone should do the measurement.” Passive is formed by inserting -l into the verb stem (yap- → yapıl-) and then adding the necessity suffix -malı.

What does the suffix -malı in yapılmalı express?

The suffix -malı (or -meli after vowels) expresses necessity or obligation—“must,” “should,” or “need to.” So yapılmalı means “it must be done” or “it should be done.”

Why is there no explicit subject in Ölçüm doğru yapılmalı?

Turkish often omits the subject in general or impersonal statements, especially in instructions or rules. Here the agent is unspecified—“(one) should do the measurement correctly.”

Why is ölçüm not in the accusative case (i.e., why no -ü ending)?

In a passive construction the original object becomes the grammatical subject and therefore stays in the nominative case. That’s why ölçüm remains unmarked.

Can I change the word order, for example say Doğru ölçüm yapılmalı?

Yes. Turkish word order is flexible. Both Doğru ölçüm yapılmalı and Ölçüm doğru yapılmalı convey “the measurement should be done correctly.” The adjective doğru (“correct”) can precede the noun or be placed before the verb in this type of sentence.

How would I express “we should measure correctly” instead?

You’d switch to an active construction with a personal subject:
Biz ölçümü doğru yapmalıyız.
Here ölçümü takes the accusative case as the object of yapmalıyız (“we should do”), and biz is the explicit subject “we.”