Δεν ξέρω τι ισχύει σήμερα, αλλά θα ρωτήσω, για να μην γίνει παρεξήγηση.

what

Breakdown of Δεν ξέρω τι ισχύει σήμερα, αλλά θα ρωτήσω, για να μην γίνει παρεξήγηση.

• δεν: not
• σήμερα: today
• αλλά: but

Questions & Answers about Δεν ξέρω τι ισχύει σήμερα, αλλά θα ρωτήσω, για να μην γίνει παρεξήγηση.

Why is the negation Δεν used here, and not Μην?

Δεν is used to negate verbs in the indicative (statements of fact, what you know/don’t know): Δεν ξέρω.
Μην is used mainly with the subjunctive, imperatives, and “don’t let…” type meanings (and it appears later: για να μην γίνει).

What form is ξέρω?

ξέρω is present indicative, 1st person singular: “I know.”
So Δεν ξέρω is “I don’t know” in a neutral, everyday way.

What is τι doing in Δεν ξέρω τι ισχύει σήμερα?

It introduces an indirect question (embedded question): “I don’t know what applies/is true today.”
Greek uses τι very naturally in indirect questions like this (similar to English “what” in “I don’t know what’s going on”).

Why is the verb ισχύει used—what does it imply?

ισχύει literally means “is valid / holds / applies.”
It’s often used for rules, policies, information, arrangements, schedules, etc. So it can sound like: what the current rule/status is.