Learn Hardcore French: Dans ce champ, un cheval court et une vache regarde tranquillement. - In that field, a horse runs and a cow watches quietly.

ce
- masculine singular noun starting with a consonant: ce champ, ce livre
cet
- masculine singular noun starting with a vowel or mute h: cet arbre, cet homme
cette
- feminine singular noun: cette maison, cette vache
ces
- any plural noun: ces champs, ces vaches

So cette champ is incorrect because cette must be followed by a feminine noun, and champ is masculine.

Why do we say dans ce champ and not something like à ce champ or sur ce champ?

Dans is the normal preposition for in a field, because the idea is being inside the boundaries of that field.

dans ce champ = in this field (inside the area)
sur ce champ would mean literally on top of this field, which doesn’t fit here. You might say sur le champ in other fixed expressions, but not for location inside a field.
à ce champ is not idiomatic modern French for “in this field.”

So for physical location inside a delimited area (a room, a field, a box, a park, etc.) French typically uses dans:
dans ce champ, dans cette boîte, dans le parc.

Why do we have un cheval and une vache instead of le cheval and la vache?

Un / une are indefinite articles, like a / an in English. They’re used when you talk about a horse and a cow that haven’t been specifically identified before.

un cheval = a horse (some horse)
une vache = a cow (some cow)

If the speaker and listener both know exactly which horse and cow are meant (for example, you already mentioned them), you would use the definite articles:

le cheval = the horse
la vache = the cow

So:

Dans ce champ, un cheval court… = In this field, a horse is running… (introducing it)
Dans ce champ, le cheval court… = In this field, the horse is running… (one you already know about)

There are two animals in the sentence. Why is it un cheval court and not un cheval courent?

Each verb has its own subject, and both subjects are singular:

un cheval court (subject: un cheval, singular)
une vache regarde (subject: une vache, singular)

So both verbs must be 3rd person singular:

il / elle court
il / elle regarde

You would only use a plural verb if the same verb applied to both animals together, with a plural subject:

Un cheval et une vache courent. = A horse and a cow are running.
(subject is un cheval et une vache → plural → courent)

In the given sentence, the structure is:

un cheval court
et
une vache regarde tranquillement

Two independent little clauses, each with a singular subject and a singular verb.

Should it be une vache regarde or une vache regardent?

It must be une vache regarde, because une vache is singular.

Conjugation of regarder in the present:

je regarde
tu regardes
il / elle / on regarde
nous regardons
vous regardez
ils / elles regardent

Here the subject is une vache → equivalent to elle → elle regarde.

Regardent is only used with a plural subject:
Les vaches regardent, Elles regardent, Un cheval et une vache regardent, etc.

Why is it tranquillement and not tranquille?

Because tranquillement is an adverb, and you need an adverb to modify a verb like regarder.

tranquille is an adjective: it describes a noun or pronoun:
- La vache est tranquille. = The cow is calm.
- Une vache tranquille regarde le cheval. = A calm cow is watching the horse.
tranquillement is the adverb formed from tranquille:
- La vache regarde tranquillement. = The cow is quietly / calmly looking.

In French, most adverbs of manner are formed with ‑ment from an adjective:

lent → lentement (slow → slowly)
calme → calmement (calm → calmly)
tranquille → tranquillement (quiet → quietly)

Because tranquillement modifies regarde (how the cow is looking), the adverb form is required.

Can tranquillement go in a different place in the sentence?

Yes, adverbs like tranquillement (manner adverbs: how something is done) are usually placed after the verb, but other positions are possible for nuance or emphasis.

Typical, neutral:

Une vache regarde tranquillement.
Dans ce champ, une vache regarde tranquillement.

Other possibilities:

Dans ce champ, une vache regarde tranquillement un cheval. (if you specify the object)
Une vache, dans ce champ, regarde tranquillement. (slightly more literary / marked)
Une vache regarde, tranquillement. (comma adds a little pause or emphasis on “calmly”)

What you cannot normally do is put the adverb between the subject and the verb:

✗ Une vache tranquillement regarde… (sounds unnatural in standard French)

Why is there a comma after Dans ce champ in French? Is it required?

The comma after Dans ce champ marks a fronted adverbial phrase (time/place/manner put at the beginning for emphasis or clarity). In both French and English, it is very common and stylistically natural:

Dans ce champ, un cheval court…
In this field, a horse is running…

Is it strictly required? Not absolutely, but:

Dans ce champ un cheval court… is grammatically possible but less clear and less natural in writing.
Most native writers would include the comma, especially in anything more formal than very casual notes.

So: you almost always put that comma; think of it as the default.

Could you also say voit instead of regarde? What’s the difference between regarder and voir here?

Regarder and voir are not interchangeable:

voir = to see (perception that happens more or less passively, without effort)
regarder = to look (to direct your eyes at something intentionally)

In this sentence the cow is looking calmly, so regarde is the natural choice:

Une vache regarde tranquillement. = A cow is quietly watching / looking.

If you used voir:

Une vache voit tranquillement. – Grammatically possible, but sounds odd; you rarely adverbially modify voir this way.
More natural would be something like La vache voit le cheval, but that just states the fact that she sees the horse, not that she’s watching it.

So regarder is correct because it expresses the idea of actively watching.

Why does French use the simple present (court, regarde) where English might say “is running / is watching”?

French present tense covers both:

English simple present: A horse runs.
English present continuous: A horse is running.

So:

Un cheval court. can mean either
- A horse runs. (habitual: that’s what it generally does)
- or A horse is running. (right now, in this situation)

Context usually tells you which reading is intended. To insist a bit on the “right now” aspect, you can add an expression like en ce moment, en train de:

En ce moment, un cheval court dans ce champ.
Un cheval est en train de courir dans ce champ.

But normally court and regarde are enough for both “runs / is running” and “watches / is watching.”

How is the sentence pronounced? Any tricky sounds or liaisons?

Approximate IPA and notes:

Dans ce champ, un cheval court et une vache regarde tranquillement.
/ dɑ̃ sə ʃɑ̃ | œ̃ ʃəval kuʁ e yn vaʃ ʁəɡaʁd tʁɑ̃kilmɑ̃ /

Key points:

dans → /dɑ̃/ (nasal vowel; final s silent)
ce → /sə/
champ → /ʃɑ̃/ (nasal; mp pronounced /̃/ only, p silent)
un → /œ̃/ (nasal)
cheval → /ʃəval/ (final l pronounced)
court → /kuʁ/ (final t silent)
et → /e/ (same sound as est in many accents, but different spelling/meaning)
une → /yn/
vache → /vaʃ/ (final e mostly mute, heard only as /ʃ/)
regarde → /ʁəɡaʁd/ (final e almost mute; d pronounced)
tranquillement → /tʁɑ̃kilmɑ̃/
- nasal an /ɑ̃/
- the ill here is /il/ (not like the /j/ in fille)
- final t mute

Possible but not obligatory liaison:

You may lightly link court et → [kuʁ‿e]; the t remains silent as a consonant, but the flow is smooth. No required liaisons in this sentence.