|singulier_ou_pluriel{xxx:single_item_string, xxx:several_items_string}

The |singulier_ou_pluriel filter is usually applied to assign (singular or plural) character strings depending on the return value of a tag.

Example:

Let’s say that we have the following declarations in our local_xx.php language file:

'quantity_something_one'   => 'there was 1 result returned by this loop.',
'quantity_something_more' => 'there were @nb@ results returned in this loop.'

And then we code a SPIP loop as below:

<BOUCLE_a(ARTICLES) {criteria...}>
  ...
</BOUCLE_a>
[(#TOTAL_BOUCLE|singulier_ou_pluriel{local:quantity_something_one, local:quantity_something_more, nb})]
</B_a>

-  If the loop only returns a single entry, then it will display:

there was 1 result returned by this loop. 

-  If the loop returns 36 entries, then it will display:

'there were 36 results returned in this loop.

Note that we can pass a 3^rd argument to this filter: nb, which allows us to include the actual numerical value returned by the tag inside the character string.

Attention:
This filter explicitly expects some language idioms as its arguments. You should therefore not pass it any language tags:
|singulier_ou_pluriel{module:one_item, module:more_items}
is the correct syntax;
|singulier_ou_pluriel{<:module:one_item:>, <:module:more_items:>}
is the incorrect syntax .