There is very little difference between below and below. Both are prepositions, which means that something is lower or less than something else. Usually below it is used more widely than below and if there is any concern as to which word to use the safe choice is below.
The word below can be used when someone or something is under control, under a new administration or under the command of. These scenarios give one person authority over someone and the other person is under that authority. One item is lower or under the control of another. Below is used to mean less than in numerical terms. For example, there were fewer than five students in the class.
There are numerous expressions that use the word below before another word:
Under stress: feeling pressured by an emotional situation.
Under the influence of someone: be controlled by another person.
Under construction: construction works that are not finished.
Under a spell: be haunted or controlled by magic.
Under pressure: feeling pressured to make a decision.
Below is very close in meaning to below and since both are prepositions, both are used in the same way to describe the position of something or someone. It is then used more frequently to describe objects at different levels, for example, images on a wall. One image can be below the other. Temperatures and water levels are recorded below a certain height.
It is then used with words such as sea level, surface and poverty line all the measurements of numerical levels.
- Below the surface, just below the top level
- Below the poverty line, just below the line of being poor and needy.
- Below sea level – land that is below sea level.
The opposite of below is above that shows once more how this word is linked to the distance between things, while the opposite of below is more of showing the word to be part of a cover. When you go to sleep, you lie under the sheets.
Both words have some interesting idioms.
Debajo de la sal: si estás ‘debajo de la sal’ estás siendo colocado en una posición por debajo de tu valor. En la Edad Media, la sal, un producto valioso, se colocaba en el medio de la mesa. El jefe de la mesa era la persona de más alto rango, así que si te colocaran más abajo en la mesa debajo de la sal, serías menos importante.
Por debajo de la media: este es un término utilizado para describir a un jugador que está jugando por debajo del número requerido de golpes en un hoyo particular en el campo de golf. También describe cómo se siente una persona si no está realmente bien.
Debajo del cinturón: un término que proviene del boxeo. No se permite golpear debajo del cinturón. Se dice que un comentario poco amable está por debajo del cinturón: injusto.
Under the breath: speak softly so that the comment is not really heard.
In the weather: it does not feel very good.
The golfer who plays below average could be feeling bad. Below and below they look very similar, could they be interchangeable? Yes, it is possible to play at par but not under the weather!
 Difference between below and below. wwwenglishgrammer.org. June 6, 2011 English grammar.org.27 / 10/2017
 En vs. Below.www.pearsonlongman.com.Pearson Education.inc 10/27/2017
 “Image credit: https://ell.stackexchange.com/questions/31595/difference-between-beneath-and-under”