Profundo vs. hondo
The Spanish words 'profundo' and 'hondo' both translate to 'deep' in English. Although they are often used interchangeably, there is a small difference between them depending on the context.
Profundo
'Profundo' is usually used to describe the physical or metaphorical depth of something in terms of its internal extent, such as thoughts, feelings or various qualities.
El océano es muy profundo.
(The ocean is very deep.)
Se sumergió en profundos pensamientos.
(She submerged herself into deep thoughts.)
Es una persona con profundas convicciones religiosas.
(He is a person with deep religious convictions.)
Hondo
'Hondo' is primarily used to describe physical depth from the surface downwards, such as a well or a valley. It can sometimes refer to emotional depth, although it's less common than 'profundo'.
El pozo es muy hondo.
(The well is very deep.)
Vierte la fruta en una cazuela honda y cúbrela con agua.
(Pour the fruit in a deep pan and cover with water.)
Sus palabras me hicieron sentir un dolor hondo.
(His words made me feel a deep pain.)
Summary
'Profundo' and 'hondo' both mean 'deep', but while 'profundo' can refer to the depth of abstract concepts or feelings as well as physical depth, 'hondo' is typically used for describing the physical depth from the surface of objects or spaces.