# vspace doesn't work properly

I am using \vspace{3mm} for separating the paragraphs in my article (\documentclass[12pt, a4paper]{article}). But most of the time it doesn't work properly. Sometimes it just puts the first few words/sentence of the following paragraph at the end of the previous one.

I need something like this:

Hello world.
\vspace{3mm}
How are you? I am good.


And sometimes I get this output:

 Hello world. How are you?

I am good.


Do you know why? Or do you know another command that does the same?

• try separating the parts you wish to have vertical space with an empty line just after \vspace command... also a \noindent on the start of the next line could be needed – koleygr Mar 11 '19 at 8:49
• @koleygr if you fond yourself needing \noindent it is almost always a sign that the markup is wrong somewhere.... – David Carlisle Mar 11 '19 at 8:50
• Mary if you want vertical space between paragraphs then you should set \parskip in the preamble, not add \vspace between each paragraph. – David Carlisle Mar 11 '19 at 8:53
• You are right... just tied to give more options because thought for the moment that the OP would not like to have indented the following text... Also, I use \noindent some times, but mostly inside some of my commands (of bold descriptions etc) and I don't think it is a mistake... Anyway... In your answer I would prefer the \vspace in the end of the first sentence and not in the beggining of the second just because I can read it easier (+1 by the way) – koleygr Mar 11 '19 at 8:56
• [Unchecked] You can use Hello world\\[3mm] How are you. However, I suggest you not to do that. – user156344 Mar 11 '19 at 9:07

You have

Hello world.
\vspace{3mm}
How are you? I am good.


Which is a single paragraph, so the \vspace is added after the current line, probably after good.

You could use

Hello world.

\vspace{3mm}
How are you? I am good.


Bur you should almost never need explicit spacing within the document anyway.