Multitud vs. muchedumbre vs. público

The Spanish words 'multitud', 'muchedumbre', and 'público' can all be translated as 'crowd' in English. However, they convey slightly different nuances and are used in different contexts.

Multitud

'Multitud' is used to refer to a large number of people or things located in the same place. It translates directly as 'crowd' but has a connotation of multitude or abundance.
Había una multitud de personas en el concierto.
(There was a crowd of people at the concert.)
La multitud de problemas dificultó la solución.
(The multitude of problems impeded the solution.)

Muchedumbre

'Muchedumbre' also translates as 'crowd'. However, it often implies a more disorderly or uncontrolled mass of people.
La muchedumbre se agolpaba ante la puerta del estadio.
(The crowd was crashing against the stadium's door.)
"Evita las muchedumbres", le aconsejó su médico.
("Avoid crowds", her doctor advised her.)

Público

'Público' can mean 'public', but when used in a context resembling 'crowd', it tends to indicate an audience or a group of spectators, often in an organized event or occasion.
El público aplaudió durante varios minutos después de la actuación.
(The audience applauded for several minutes after the performance.)
El mago cautivó al público con sus trucos extraordinarios.
(The magician captivated the audience with his extraordinary tricks.)

Summary

While 'multitud', 'muchedumbre', and 'público' can all be translated into English as 'crowd', each word has unique implications. 'Multitud' conveys an abundance, which may refer to people or things; 'muchedumbre', though it describes a large number of people, carries with it an idea of disorderliness; and, 'público', though it may describe a crowd, is more often used in contexts where English speakers would use 'audience'.