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<p>This looks identical to what in Japanese and a few other places
nearby are called 'sentence-final particles', though that's far
from a satisfying name for that typological category. These
markers serve primarily to inform listeners of the purpose behind
speaking the sentence:<br>
</p>
<p><i>aru</i> 'it's there' (no SFP, sort of neutral)<br>
<i>aru yo</i> 'it's there' (which I don't think you knew but I
think you should know)<br>
<i>aru ne</i> 'it's there, isn't it' (I think I'm right but I'd
like to confirm / I'm fairly sure you agree with me)<br>
<i>aru wa!</i> 'what the heck, it's there!' / 'of course it's
there, are you stupid?'<br>
<i>aru kedo</i> 'it's there' (but I'm not sure if that's relevant
information to you or not)<br>
<i>aru tteba</i><i>!</i> 'I'm telling you, it's there' (why won't
you listen to me)<br>
<i>aru yo ne</i> 'oh, of course it's there' (I should have
realised it earlier)</p>
<p>(note that <i>yo</i> in Japanese also doubles as a high-register
vocative - <i>shounen yo</i> 'O youth')<br>
</p>
<p>This is a category of morphemes that to my knowledge lacks any
crosslinguistic typological study; though I think it very well
needs one, as it seems to be primarily thought of as an East Asian
feature but certainly occurs elsewhere. Yale, a Papuan isolate
I've gotten to do some work with, has something apparently
directly analogous to Japanese's sentence-final particles:</p>
<p><i>bo klɛli mogo kile nɛ-l-e <b>o<br>
</b></i>1sg pig carcass leave 1sg-AUX-1sg <b>SFP</b> <br>
'I left a pig carcass (and you should be aware of this)'</p>
<p>Yale has several of these, including <i>o</i>, which seems to
mark the sentence as informing the listener of information; <i>ne</i>,
which is how Yale handles interrogative marking; <i>nawa</i>,
which indicates that the speaker is wondering whether the contents
of the sentence might be true (or what the answer to the
sentence's content question is); and <i>fɛ</i>, which directs the
listener's attention towards a state described by the sentence (<i>hi
wɛsibi wa kibo mɛlɛ fɛ </i>'look, the food's gone bad').</p>
<p>I wouldn't be surprised if Heyo also has a larger category of
these things that includes more than just the <i>o</i> you've
noticed.<br>
</p>
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