Similar to how suffixes indicate number and person for D'ni verbs, prefixes indicate different tenses. So far, we've been working with verbs in the simple present tense. This is the most basic tense in D'ni and we recognize it by the absence of prefixes. When we place Do– in front of a conjugated simple present tense verb, the tense changes to present progressive. Do– may appear as a prefix on any verb, as long as that verb is conjugated; it will never appear in the infinitive.
The simple present tense is a plain statement of action or being: lonEt, they discover; reano remen, the water flows. When the present tense verb becomes progressive, it describes an action that is currently in progress, that is happening right now in the present: DoselEt, they are writing (at this moment); Atrus DoeDeren, Atrus is sleeping (right now as we speak). These present progressive verbs, when translated into English, will always take the form of subject + to be + verb-ing — the -ing ending in English is often a clue that you have a progressive tense.
One common mistake that is made when translating from English to D'ni is to see a present progressive verb — you are dying — and try to translate it as a form of Ken, to be, plus another verb, resulting in something like Kenem DomanSU. This is an incorrect translation — you are dying cannot be separated out into two verbs, you are + dying. Where English needs to use helping verbs, forms of to be and to have to express complex verb forms, D'ni is capable of doing so with a single word.
When translating complex verb forms like our present progressive example, You are dying, it is best to step back, figure out the verbal idea (second person singular, present progressive tense) and then translate into D'ni: DomanSUem. This is the proper translation; the root of the verb is manSU, die, the personal ending – em tells us the verb is second person singular, and the tense prefix Do– tells us that the tense is present progressive.