Difference between a sonority and a chord?

I have seen both terms used in many text books. Do they imply the same thing, or are they different?

I hear Sonority being used to describe more err 'modern' harmonies... that and passing harmonies i.e. polyphonic writing

The context is what we generally use to distinguish "sonority" from "chord." In the context, a chord falls under the broader scope of sonority. A chord is a triad or triad + extensions in the tonal harmonic language. The broader scope of sonority includes all "chords" and non-tertian harmonic expressions. So, for example, we might say that a non-tertian (meaning, a group of pitches sounding at the same time  that are NOT built on thirds) harmony is a "sonority" but not necessarily a "chord" in the traditional sense. 

Personally, I'd expand "chord" to include any single moment where multiple pitches are sounding at once, regardless of the intervals used to create the chord. I would expand sonority to include all the chords that make up the musical "syntax" representative of the style of music. Some theorists refer to it in this way already, so I think it holds weight. But we're speaking in semantics here, which usually displeases me. I'd rather just write music and be done with arguing over how to use words to describe it. What do we learn from arguing over terminology anyway?

A Chord is three or more tones played at the same time. The intervals between the notes are irrelevant.

A sonority is a chord's voicing. In this case, the intervals between the notes are relevant.

There are plenty of different approaches to these terms. It all depends on context.

In this "non-tonal" language of music, we often refer to "chords" as sonorities because the chord itself cannot be -defined- in relation to another chord the way it can be in tonal music. Ergo, it makes no sense to call a chord "any vertical grouping of three or more pitches" in the context. Tertian harmonies are so common, a trained eye can usually determine what the chord is based on its placement in the progression alone. This is not usually the case in non-tertian harmonies because each and every note of a sonority requires us to analyze each interval occurring within the sonority.

So, yes, as Tokkemon states, a chord is sometimes referred to as "any vertical grouping of three or more notes, regardless of interval" (like I said, theorists tend to vary their usage here) but that's often not how it applies when we actually study music. Once we learn basic I-V-I hierarchy, chord extensions in tertian harmony, and modality in general, the mystery is gone. There is little if any need to analyze the "sonority" of a tertian harmony at that point - we know what it is by looking at the tertian harmonic material around it. Thus, I don't bother referring to non-tertian harmonies as "chords" because of the need to understand the sonority when we're no longer in familiar, tertian waters. The usage of both words depends on context.

Even Wikipedia seems to be onto what I'm talking about here... http://en.wikipedia.org/wiki/Sonority

Sonority is any vertical combination of any number of pitches. Chord is three or more pitches sounding together, no matter if they are part of tertian or quartal/quintal harmony. Secundal chords (clusters) may be listed here, too, but I prefer to exclude them for obvious reasons. However, don't forget that dyads may function as incomplete chords.

Sonority is any vertical combination of any number of pitches. Chord is three or more pitches sounding together, no matter if they are part of tertian or quartal/quintal harmony. Secundal chords (clusters) may be listed here, too, but I prefer to exclude them for obvious reasons. However, don't forget that dyads may function as incomplete chords.

*points*

Semantics for the win!