Cum tonitrus auditur, mater infantem in gremio tenet et leniter consolatur.

Here cum means when or whenever. It introduces a time clause:

Cum tonitrus auditur = When thunder is heard

Because the verb is in the indicative (auditur), this is a straightforward temporal clause, not a more literary cum clause with the subjunctive.

Auditur is the present passive indicative of audire, meaning is heard.

Latin often uses a passive expression where English might say either:

• thunder is heard
• one hears thunder
• people hear thunder

The sentence does not name who hears the thunder, so the passive works naturally.

Tonitrus is nominative singular, and it is the subject of auditur.

So the structure is:

• tonitrus = the thing being heard
• auditur = is heard

Even though English often treats thunder more like a mass noun, Latin here presents it as the subject of the passive verb.

Latin has no articles. There is no direct equivalent of English the or a/an.

So:

• mater can mean mother or the mother
• infantem can mean an infant or the infant
• tonitrus can mean thunder or the thunder

You decide from the context which English article sounds best.

Infantem is accusative singular because it is the direct object.

It is the one whom the mother:

• tenet = holds
• consolatur = comforts

So one accusative noun can go with both verbs:

mater infantem tenet et consolatur = the mother holds and comforts the infant

Because consolatur is a deponent verb.

Deponent verbs:

• have passive forms
• but active meanings

So consolatur looks passive, but it means she comforts, not she is comforted.

This is very common in Latin, and it is something English speakers usually have to get used to.

Because in can take different cases depending on the meaning:

• in + ablative = in/on a place, showing location
• in + accusative = into/onto a place, showing motion toward

Here the baby is already in the lap, so Latin uses the ablative:

in gremio = in the lap

If there were movement into the lap, you would expect the accusative instead.

Leniter is an adverb, meaning gently or softly.

It describes how the mother comforts the infant:

leniter consolatur = she gently comforts

English speakers sometimes expect another adjective here, but Latin needs an adverb because it modifies the verb, not the noun.

Latin word order is much more flexible than English word order because the endings show each word’s function.

A very literal order is:

When thunder is heard, the mother the infant in her lap holds and gently comforts.

That sounds strange in English, but it is normal enough in Latin. The sentence begins with the cum clause to set the scene, and the main clause then gives the mother’s actions.

The present tense here gives a sense of a general situation or habitual action:

• auditur = is heard
• tenet = holds
• consolatur = comforts

So the sentence can mean something like Whenever thunder is heard, the mother holds the infant in her lap and gently comforts him or her.

Latin often uses the present this way for something regular, vivid, or generally true.