Ruban vs. nœud
While both 'ruban' and 'nœud' are related to decorative elements, they have distinct meanings in French.
Ruban
'Ruban' means ribbon, which is a long, narrow strip of fabric used for decoration or fastening.
Elle a attaché ses cheveux avec un ruban bleu.
(She tied her hair with a blue ribbon.)
Le cadeau était enveloppé d'un joli ruban doré.
(The gift was wrapped with a pretty golden ribbon.)
Nœud
'Nœud' means knot or bow, which is a fastening made by tying a piece of string, rope, or fabric.
Il a fait un nœud de cravate parfait.
(He tied a perfect necktie knot.)
Le chien portait un joli nœud rouge autour du cou.
(The dog wore a pretty red bow around its neck.)
Summary
In summary, 'ruban' refers to the ribbon itself, while 'nœud' is the knot or bow made with the ribbon or other material. A 'ruban' can be used to make a 'nœud', but they are not interchangeable terms.