Adivinar vs. conjeturar
The Spanish infinitive verbs 'adivinar' and 'conjeturar' both translate to 'to guess' or 'to make a guess' in English. However, they are not interchangeable and have some contextual differences in usage.
Adivinar
'Adivinar' is usually used when the guess involves solving or predicting something, often something that is hidden or unknown. It can be akin to guessing a riddle or fortune telling.
Vamos a jugar un juego: tienes que adivinar el número en mi cabeza.
(Let's play a game: you have to guess the number in my head.)
El mago puede adivinar tu futuro en las cartas.
(The magician can guess your future in the cards.)
Conjeturar
'Conjeturar' tends to imply an educated guess based on observations or evidence. It is closer to the concept of speculation or conjecture.
Mi profesor conjeturó que probablemente llovería mañana debido a las nubes oscuras hoy.
(My teacher conjectured that it might rain tomorrow due to the dark clouds today.)
Los científicos están conjeturando sobre los efectos del cambio climático.
(Scientists are conjecturing about the effects of climate change.)
Summary
'Adivinar' is typically used for guesses related to figuring out or predicting something unknown, while 'conjeturar' is often used for informed guesses drawn from evidence or observations.