While δεῖ can mean (s)he/it lacks, this form is frequently used IMPERSONALLY in the 3rd person singular to mean it is necessary. This construction is often complemented with an infinitive. For example:
- δεῖ ταῦτα ποιεῖν.
- It is necessary to do these things.
While δοκεῖ can mean (s)he/it seems, this form is frequently used IMPERSONALLY in the 3rd person singular to mean it seems (good/best). This construction is often complemented with a dative. For example:
- ὡς ἐμοὶ δοκεῖ…
- As it seems to me (ἐμοί)…