I know that in Biblical Hebrew (and presumably other varieties), we see the construct "noun adjective", with the noun unodified, such as "parah adamah" (red heifer). We also see the noun-chain construct, "noun noun", which usually means "noun (of) noun", and in that case the first noun is modified: "eish*et* chayil" (woman of valor), "birk*at* kohanim" (priestly blessing, but literally blessing of priests).
During yesterday's torah reading (Rosh Chodesh) I noticed both olah tamid and olat tamid, but I don't see why the grammar would be different between the uses. The former is what I'm used to seeing, for example in Bamidbar 28:3:
וְאָמַרְתָּ לָהֶם--זֶה הָאִשֶּׁה, אֲשֶׁר תַּקְרִיבוּ לַיהוָה: כְּבָשִׂים בְּנֵי-שָׁנָה תְמִימִם שְׁנַיִם לַיּוֹם, עֹלָה תָמִיד.
But a little later we see (in 28:6):
עֹלַת, תָּמִיד--הָעֲשֻׂיָה, בְּהַר סִינַי, לְרֵיחַ נִיחֹחַ, אִשֶּׁה לַיהוָה.
I see the comma there (which was not in the siddur I was following along in yesterday). Punctuation, of course, is editorial. In both cases the text seems to be describing a continual olah (burnt-offering). And later, in 28:10, we see another olat formation without any complicating punctuation:
עֹלַת שַׁבַּת, בְּשַׁבַּתּוֹ, עַל-עֹלַת הַתָּמִיד, וְנִסְכָּהּ
What distinguishes the cases that use the olah formation from the ones that use the olat formation? They all look the same to me, semantically; does the syntactic difference mean something?