Use of the word "praxis"?

According to dictionary.reference.com the word praxis means:

practice, as distinguished from theory; application or use, as of knowledge or skills.

I recently saw another stackexchange post ^{now deleted}, which used praxis in place of practice.

When it interferes with one's chosen religious praxis.

Is this a proper usage of the word?

The word praxis is definitely an extremely formal academic word. Using it in general prose elevates that prose to a formal academic style. Some people may be taken aback by use of the word, which is likely unfamiliar to many.

There are just 454 total incidences of praxis in the Corpus of Contemporary American English, 394 of them in academic texts, where it occurs with a frequency of 4.75 incidences per million words. In texts for general audiences, like magazines, newspapers, and fiction, it occurs with a frequency of 0.24 incidences per million words, which makes it about as common in those contexts as the word limn, which the Baltimore Sun recently used in a headline, to some uproar. It did not occur at all in the corpus of spoken English.

That takes care of the word praxis itself, but what about the term religious praxis? Here are the top 20 collocates—words that frequently appear nearby—with frequency of incidence near praxis from the Corpus of Contemporary American English:

1   THEORY         26
2   II             18
3   THEOLOGY       15
4   CHRISTIAN      13
5   SOCIAL         13
6   POLITICAL      12
7   ANALYSIS       10
8   MUSIC          10
9   EXAMINATION    9
10  TESTS          8
11  TEST           7
12  FEMINIST       6
13  STUDIO         6
14  SCORES         6
15  FORM           6
16  CHURCH         6
17  PRIMACY        5
18  THEOLOGICAL    5
19  ECOLOGICAL     5
20  REVOLUTIONARY  5

I see a few themes of words here:

• religion (theology, christian, theological, church)
• examination (examination, tests, test, II—“Praxis II” seems to be the name of a test)
• music (music, studio, scores)

Here are some examples of praxis being used in a religious context:

The character of these reflections in Kasper's 1962 article on Vatican I, written as a 29-year-old priest-theologian, has echoes in his 1999 article on the theology and praxis of the bishop's office, written five years after becoming the bishop of Rottenburg-Stuttgart.

He has given an increasingly important place to praxis in theology, indicating that all theory must give rise to transformative praxis.

This underscores the praxis of the church as a distinct society, constituted by peace.

The word religious itself as a collocate is just outside the top 20, with 4 incidences, but it is not absent from the corpus. Here is an example from Commentary Magazine, in an article titled “The Madoff Scandal and the Future of American Jewry”:

Samuel G. Freedman, the New York Times veteran among whose books is the provocative Jew vs. Jew, wrote powerfully about the manner in which the power elite of Modern Orthodoxy had accepted Madoff as one of its own, even though Madoff was himself not Orthodox. According to Freedman, the connections in this insular world were intense:

Their leaders and members overlap like a sequence of Venn diagrams. They are bound by religious praxis, social connection, philanthropic causes.

Religion is certainly one of the topics that the word praxis is most commonly used in, so in the right context, the term religious praxis is, as far as I am concerned, perfectly proper to use.

"Religious practice" is far more common than "religious praxis" (500 000 vs. 15 000 results in Google).

In fact, I've rarely seen "praxis" used by native English speakers in any context. I've heard it most commonly used by German speakers to mean "work placement", the equivalent of "stage" in French.