Pty is not a word you drop into a sentence. It is letters written after a company name in Australia, New Zealand, and South Africa. They stand for proprietary, and in this use that means a private company: the shares are not sold to anyone on the open market the way a big listed company’s shares are. You almost always see it locked to Ltd — Chen & Co Pty Ltd — on vans, invoices, shop windows, and letterheads. That is their way of marking what British English marks with Ltd and what people in Taiwan mark with 有限公司. You read it as the letters P-T-Y, or you just say the company name and skip the tail. Though actually, Americans do not use Pty at all; they write Inc or LLC for a similar job. It is paperwork English, not spoken English, and it tells you where the company is from as much as what kind it is.