# Question about the preposition "ab/ā"

**URL:** <https://www.textkit.com/t/question-about-the-preposition-ab-a/31160>\
**Category:** Learning Latin\
**Created:** [May 10, 2026, 1:38am UTC](https://www.textkit.com/t/question-about-the-preposition-ab-a/31160 "2026-05-10T01:38:33Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![xmetamorphosesx](https://www.textkit.com/user_avatar/www.textkit.com/xmetamorphosesx/32/1288_2.png) [@xmetamorphosesx](https://www.textkit.com/u/xmetamorphosesx)\
**Post date:** [May 10, 2026, 1:38am UTC](https://www.textkit.com/t/question-about-the-preposition-ab-a/31160/1 "2026-05-10T01:38:33Z")

</div>

I’m doing the exercises from Chapter 21 of Familia Romana (LLPSI).

In Exercitium 2, item #12:

Active: Fulgur caelum illūstrāvit =

My wrong answer (Passive): “Caelum ā fulgure illūstrātum est.”

Correct answer: “Caelum fulgure illūstrātum est.”

Why is the preposition “ab/ā” omitted here?

---

<div class="post-metadata">

**Author:** ![consistebat](https://www.textkit.com/user_avatar/www.textkit.com/consistebat/32/203_2.png) [@consistebat](https://www.textkit.com/u/consistebat)\
**Post date:** [May 10, 2026, 5:49am UTC](https://www.textkit.com/t/question-about-the-preposition-ab-a/31160/2 "2026-05-10T05:49:39Z")

</div>

It’s not omitted – one could even say it’s not permitted. _ab_ + abl. with a passive verb normally denotes human agents, while the bare ablative is used to denote instruments, the principal difference being that the former are conceived of as performing an action, while the latter are thought of merely as the force by means of which the event takes place. See [Allen & Greenough § 405](https://dcc.dickinson.edu/grammar/latin/ablative-agent), in particular:

> _Note 2—_ The Ablative of the _Agent_ (which requires _ **ā** _ or _ **ab** _) must be carefully distinguished from the Ablative of _Instrument_, which has no preposition ([§ **409**](http://dcc.dickinson.edu/grammar/latin/ablative-means)).
> 
> _ **occīsus gladiō** _  
> _slain by a sword_
> 
> BUT  
> _ **occīsus ab hoste** _  
> _slain by an enemy_
> 
> _Note 3—_ The Ablative of the Agent is commonest with nouns denoting _persons_, but it occurs also with names of things or qualities when these are conceived as performing an action and so are partly or wholly _personified_, as in the last example under the rule.

The “last example under the rule” is this:

> _ **nē virtūs ab audāciā vincerētur** _ (Sest. 92)  
> _that valor might not be overborne by audacity_
> 
> (_ **Audācia** _ is, in a manner, _personified_ here.)

---

<div class="post-metadata">

**Author:** ![xmetamorphosesx](https://www.textkit.com/user_avatar/www.textkit.com/xmetamorphosesx/32/1288_2.png) [@xmetamorphosesx](https://www.textkit.com/u/xmetamorphosesx)\
**Post date:** [May 13, 2026, 1:14pm UTC](https://www.textkit.com/t/question-about-the-preposition-ab-a/31160/3 "2026-05-13T13:14:38Z")

</div>

Thanks for the explanation and the link, they really helped!