If in English you can insert the word ‘that’ after the verb of fearing, then Latin uses the ne + subjunctive construction. As in, if your fearing verb introduces a clause with its own verb, you’ll use ne + subjunctive.
For example:
timeo ne hostes mox adveniant.
I fear (that) the enemy may arrive soon.
The tense of the subjunctive follows the sequence of tenses:
Primary Sequence
Referring to the present or the future: present subjunctive
Referring to the past: perfect subjunctive
Historic Sequence
Referring to the same or a later time: imperfect subjunctive
Referring to something that has already happened: pluperfect subjunctive
vereor ne illa me videat.
I am afraid that she will see me.
metuebam ne illa me videret.
I was afraid that she would see me.
The negative of ne is formed by ne + a negative adverb, or ut.
timui ne mihi auxilium non ferres.
I was afraid that you would not bring me help.
timebant ut inveniretur.
He was afraid that he might not be found.
The ne + subjunctive is also used when fear is implied rather than stated: ‘there is a danger that x will happen’, ‘I did x to avoid y.’ For example:
periculum est ne soror tua serius adveniat.
There is a danger that your sister will arrive too late.