Samuel said:
<tr>
<td><p>Achromaat</p></td>
<td><p>De persoon mist het kleuren zien ten gevolge van het
ontbreken van alle kegeltjes.</p></td>
</tr>
Are the paragraphs okay or are they not needed?
A single word hardly constitutes a paragraph. A paragraph is "a subdivision
of a written composition that consists of one or more sentences, deals with
one point or gives the words of one speaker, and begins on a new usually
indented line", to quote
http://www.merriam-webster.com/dictionary/paragraph
It might be argued that the defining text in the second cell is a paragraph,
but it's really just part of a sentence, implying the word being defined as
the subject and some predicate expression like "is" or "is defined as". I
think this even applies to those cases in your table where the second-column
cell contains complete sentences. They still don't constitute a _paragraph_,
i.e. a relatively self-contained passage of text - at least the term being
defined needs to be implied here.
Of course this is mostly just theoretical, since correct semantics of markup
has little impact on the practical properties of an HTML document. Still,
why should we use wrong markup when we can easily, and often easier, use
more proper markup?
Is there a reason to use/not use paragraphs within a <td>?
It's hard to see how it could do any good.
The default top and bottom margins of <p> elements might cause some
undesirable formatting. Oddly, you seem to have set them to zero, except for
top margin, causing some waste of space. Just omitting <p> markup is the
best approach. If you really want the extra spacing you have now, you can
easily create it using padding-top for said:
My table is to found here, just in case one needs to see the bigger
picture:
http://oukjeweb.com/tabel.html
I have to contradict myself a bit. Sometimes in tables of definitions like
this*), the defining expression is so long and complicated that it should
maybe be divided into two or more paragraphs. For example, your definition
for "gezichtsscherpte" is fairly long and would probably benefit from a
division into paragraphs. But then a <td> would contain two or more <p>
elements whereas other cells in the same column would have just text
content.
I'd respond by asking "So what?" When you define terms, sometimes the
defining expression can be a single word (like a more common synonym),
sometimes a few words, or an almost complete sentence, or even more - maybe
several paragraphs. It could also be a list, or contain a list, or maybe an
image. There is no reason why such variation, when it exists (it might be
inferior presentation style, but that's debatable, and not really relevant
here), should not be reflected in the markup. If the cells contain really
different types of stuff, they can well contain different markup elements.
*) A table is good markup. Theoretically you could additionally use <dfn>
markup for the term being defined or alternatively use <dl> for the whole
stuff, but don't bother - such markup approaches have drawbacks and they
hardly achieve anything, in this world where web browsers and robots are
mostly semantically ignorant, despite all the idle babbling about "semantic
web". There is no really adequate markup for definitions, still less sets of
definitions, in HTML, and using a two-column table is quite OK.