ὑπόνοια δεινόν ἐστιν ἀνθρώποις κακόν → suspicion is a terrible evil for people

[gregroz]

Homework phrase from class where we learned only verbs and 1st & second declension (no adjectives yet).
I'm not sure about the δεινόν and κακόν - which cases/persons and weather nouns or adjectives are they.

Ὑπόνοια δεινόν εστιν ανθρώποις κακόν (Meander) = ???

I know it is similar to:
ὕπνος δεινὸν ἀνθρώποις κακόν (Menander) = sleep is a terrible<fearsome> evil for humans <to men>
(web translations, not mine, but look legit)

and similar to
Ἡ γλῶσσα πολλῶν ἐστιν αἰτία κακῶν (Meander) = Language is the cause of many evil things
(classroom translation)

I learn it in Slavic language, so English translations are not enough to understand the cases in these sentences

I would translate
Ὑπόνοια δεινόν εστιν ανθρώποις κακόν.
as:
Suspition(fem Nom) bad/fearful/terrible (? Acc?) is [to the] people (m plur. Dat) evil (neut.N/A /masc A)
=Terrible (=very exagarated?) suspition is evil to/for people.

But the above other examples of Menander and how they are translated make me doubt.

The rough sense is clear: suspition is bad for the men. But rough is not enough :(
I would appreaciate learning in how many ways can this be understood properly. And how it can look with all the proper articles and prepositions - if someone would be that kind to help me :)

[billberg23]

All good questions, gregroz.  Here the neuter singular adjective κακόν ("evil") is treated as a noun ("an evil thing").  You can do that with almost any neuter adjective (καλόν "a beautiful thing," αἰδοῖον "a shameful thing," πλήσιον "a close thing," etc.).  Suspicion is what kind of evil?  A terrible evil!  Suspicion is a terrible evil for people/humans.
Sophocles famously does this with the neuter plural adjective δεινά in the Antigone, verse 332: πολλά τὰ δεινά — "many are the terrible (things)."   

[gregroz]

Thank you very much.
Now I'm only not sure what form δεινόν is. Same kind of noun as κακόν? As it only seems to be with that ending next to female subject-noun...

My understanding is now, that
Ὑπόνοια δεινόν ἐστιν ἀνθρώποις κακόν

I could expand as (something like):
Ἡ ὑπόνοια [τὸ??] δεινόν ἐστιν τοῖς ἀνθρώποις τὸ κακόν

And rearrange to:
Ἡ ὑπόνοια τὸ δεινόν τὸ κακόν τοῖς ἀνθρώποις (ἐστιν).
for it to mean the same.

Am I very far off?

[billberg23]

Τhe word δεινόν is simply a neuter singular adjective (δεινός, δεινή, δεινόν) modifying the neuter singular noun κακόν.  If it were feminine to modify ὑπόνοια, it would have to be δεινή. 
Re-arranging Ὑπόνοια δεινόν ἐστιν ἀνθρώποις κακόν to fit English word order, we get Ὑπόνοια ἐστιν δεινόν κακόν ἀνθρώποις , "Suspicion is a terrible evil to people."