Testator non modo abest, sed ne signator quidem adest.

This is a common Latin pairing.

• non modo = not only
• sed = but
• ne ... quidem = not even

So the whole pattern means something like:

• not only ..., but not even ...
• or, in smoother English, ... is not the only problem; even ... is not ...

In this sentence, the second half is stronger than the first. Latin often uses this structure to build emphasis step by step.

Because the second clause is negated in a different way.

• abest = is absent
• adest = is present
• ne signator quidem adest = not even the signator is present

So although the verbs are opposites, the meaning comes out similarly:

• testator abest = the testator is absent
• ne signator quidem adest = even the signator is absent / not even the signator is present

Latin often does this. Instead of repeating abest, it can say not even ... is present, which is more pointed and emphatic.

Here ne ... quidem means not even.

It is a set expression. The important thing to notice is that it usually surrounds the word being emphasized.

So:

• ne signator quidem adest

means:

• not even the signator is present

The emphasis falls on signator. In other words, the sentence says that the absence is so serious that even the signator is not there.

Because in this idiom Latin normally places ne before the emphasized word and quidem after it.

So:

• ne signator quidem = not even the signator

This is a very common pattern:

• ne ego quidem = not even I
• ne ille quidem = not even he
• ne hoc quidem = not even this

So the position is not random. It is the normal way Latin marks the word being focused.

They are both third-person singular present indicative active forms.

More specifically:

• abest comes from absum, abesse = to be away, be absent
• adest comes from adsum, adesse = to be present, be at hand

Both are compounds of sum, esse.

So:

• abest = he/she/it is absent
• adest = he/she/it is present

Since testator and signator are singular subjects, singular verbs are used.

Because they are the subjects of the verbs.

• testator ... abest = the testator is absent
• signator ... adest = the signator is present

In Latin, the subject of a finite verb is normally in the nominative. That is what is happening here.

Also, Latin does not need an article, so testator can mean the testator or a testator, depending on context.

They are both agent nouns.

The ending -tor often means a person who does something.

Examples:

• testator = a person who makes a will, a testator
• signator = a person who signs or seals, a signer / signatory / witness

So the matching endings are not accidental. They are formed in a similar way.

For an English speaker, this can actually be helpful, because English has many related words from the same pattern:

• actor
• creator
• orator

No. The most common positive pattern is:

• non modo ... sed etiam ...
• not only ... but also ...

But when the second part is negative and especially emphatic, Latin can use:

• non modo ... sed ne ... quidem ...
• not only ... but not even ...

So in this sentence, the second half is deliberately stronger than a simple but also.

Yes, that would be possible Latin, but it would not mean exactly the same thing.

• sed signator quoque abest = but the signator also is absent
• sed ne signator quidem adest = but not even the signator is present

The second version is more forceful. It suggests a stronger sense of surprise or emphasis: the problem is so severe that even the signator is missing.

So the actual wording is rhetorically sharper.

It is the same basic particle, but here it is part of the fixed expression ne ... quidem.

So you should not read it here as:

• a prohibition marker
• or a purpose-clause marker by itself

Instead, read the whole unit together:

• ne ... quidem = not even

That is the safest way to understand it.

Not very literal. A word-for-word version would sound awkward.

Very literal:

• The testator is absent not only, but not even the signator is present.

More natural English:

• Not only is the testator absent, but even the signator is not present.
• The testator is absent, and even the signator is not present.
• It is not just the testator who is absent; even the signator is missing.

So when reading Latin, it helps to understand the structure first, and then turn it into natural English.

Because the verb form already contains it.

• abest already means is absent
• adest already means is present

Latin finite verbs usually include the subject ending and the tense, so you do not need a separate word like English is.

That is why a single Latin word can correspond to two or three English words.

The word order helps the emphasis unfold gradually.

• Testator comes first: the sentence starts with the person you might most expect to be present.
• non modo abest tells you that this person is absent.
• Then sed ne signator quidem raises the stakes: not just that person, but not even the signator.
• Finally adest completes the thought: the signator is not present either.

So the sentence is arranged for rhetorical impact, not just bare information. Latin often uses word order this way.