a. μὴ γράφε, like don't write, is ambiguous and may mean, according to the situation, either cease writing or abstain from writing. Commonly μὴ γράφε means do not go on writing, write no more, and is an order to stop an action already begun. In many cases, however, μή with the present imperative does not refer to the interruption of an action already begun, but to an action still in the more or less distant future against which the speaker urges resistance. Sometimes the reference to the future is directly or indirectly indicated by the context.
b. μὴ γράψῃς usually has the force of (I beg that) you will not write, (take care that you) don't write, and is commonly a complete prohibition against doing something not already begun. Sometimes, and especially in expressions of a colloquial character, μή with the aorist subjunctive marks the speaker's interruption, by anticipation, of a mental (less often of a physical) action that is being done by the person he addresses; as μὴ θαυμάσῃς ( L. 804b) in reply to an exclamation of surprise. Here the type μὴ γράψῃς often expresses impatience.
c. If μὴ γράφε elicits a reply, it is (ἀλλ᾽) οὐ γράφω, while μὴ γράψῃς is answered by (ἀλλ᾽) οὐ γράψω. Thus, μή μ᾽ ἐκδίδασκε τοῖς φίλοις εἶναι κακήν. ἀλλ᾽ οὐ διδάσκω
do not teach me to be base to my friends. But I do not El. 395, εἰ οὖν ἔχεις ἐναργέστερον ἡμῖν ἐπιδεῖξαι ὡς διδακτόν ἐστιν ἡ ἀρετή, μὴ φθονήσῃς ἀλλ᾽ ἐπίδειξον. ἀλλ᾽ . . . οὐ φθονήσω now if you can show us more clearly that virtue is capable of being taught, don't refuse, but show us. Well, I will not refuse Pr. 320c. So μὴ γράφε commonly answers γράφω, as θαυμάζω, ἦν δ᾽ ἐγώ, καὶ αὐτός. ἀλλὰ μὴ θαύμαζ᾽, ἔφη I myself am astonished, said I. Cease your astonishment, said she S. 205b, cp. El. 395. So μὴ γράψῃς answers γράψω, as in 3.140, Lys. 1036.
d. μὴ γράφε and μὴ γράψῃς are often found in closely connected clauses, as μηδαμῶς θῡ́μαινέ μοι, μηδέ μ᾽ ἐπιτρῑ́ψῃς
don't be angry with me at all, nor ruin me Nub. 1478, μήτ᾽ ὀκνεῖτε μήτ᾽ ἀφῆτ᾽ ἔπος κακόν
do not shrink from me nor utter any harsh words O. C. 731. The second prohibition may be more specific than the first, as σιώπᾱ· μηδὲν εἴπῃς νήπιον
be silent, don't say anything childish Nub. 105. Less often μὴ γράψῃς is followed by μὴ γράφε, as μὴ βοηθήσατε τῷ πεπονθότι δεινά· μὴ εὐορκεῖτε (they will say) ‘do not come to the aid of one who has suffered grievously; have no regard for your oath’ 21.211.
e. The difference between μὴ γράφε and μὴ γράψῃς is virtually a difference of tenses, the present denoting an action continuing, in process; the aorist, an action concluded, summarized. So μὴ φοβοῦ don't be fearful, μὴ φοβηθῇς don't be frightened. In maxims μή with the present imperative is preferred: μὴ κλέπτε don't be a thief, μὴ κλέψῃς don't steal this or that. μηκέτι may be used in either construction. The distinction is often immaterial, often a difference of tone rather than of meaning; sometimes too subtle for dogmatic statement.