Difference between “la ligne,” “le rang,” “la rangée”?

Question

I'm trying to understand how to refer to “a row” of something in French. Also, what preposition goes with this, and what verb? For instance, in English we might say:

The ducks were sitting in a row.

The ducks were all in a row.

There was a row of ducks.

How is such a sentiment expressed in French?

Answer 1

The adequate translation for the geometric shape is ligne here.

Les canards étaient assis en ligne.

Ils formaient une ligne.

On pouvait voir une ligne de canards.

When used in conjunction with a verb, the corresponding adverbial group is en ligne:

Ils étaient rangés en ligne.

The verb to express this is aligner used in a passive form:

Les canards étaient alignés.

Les rangs is only used to indicate that the formation is deliberately ordered (or looks like it).

On aurait dit les rangs d'une armée de canards.

Also, une rangée is one row of a (maybe fictive) bigger formation.

Plusieurs rangées de canards s'approchaient de l'étang.

Le rang has nothing to do with the actual geometry, it refers either to the position inside an ordering (which may be a spacial ordering), or to the general concept of maintaining a hierarchy or a formation.

Answer 2

As I note in my comment to Stéphane, "rang" also has the meaning of "rangée", though it is less common today. You'll find the expression "en rangs" for people arranged in several rows, and for plants in a garden or field. A course of knitting stitches is also called a "rang", as are rows of seats in a room when describing a location: "sitting in the third row" is "assis au troisième rang".

Another difference is that a "rangée" is a side by side alignment of objects (unlike a "file" where they are one behind the other, hence "maisons en rangée", rowhouses, but "file d'attente", waiting line), whereas "ligne" does make that supposition, and "rang" (at least in its original meaning) can mean either meaning. (Petit Robert 2007, s.v. "rang" & "rangée")

Answer 3

Les canards étaient en rang d'oignons

même, s'il n'y a pas de notion d'ordre particulier (la mère suivie de ses petits par exemple), c'est la traduction pour signifier que la rangée aperçue n'est pas naturelle ou habituelle,

s'ils marchaient en rang (sur une colonne) on aurait alors

une file indienne.
Les canards se dandinaient à la queue leu-leu
On peut aussi dire que la mère est suivie de ses petits qui marchent en rang d'oignons.