Used to say something is preferable or less bad compared with another option (often as マシだ). It implies a choice is not ideal but better than alternatives.
この古いパソコンでも動くなら、まだマシだ。
If this old PC still runs, that's still better.
彼の意見は間違っているが、何も言わないよりはマシだ。
His opinion is wrong, but it's better than saying nothing.
雨が降っているけど、傘があるからまだましだ。
It's raining, but since I have an umbrella it's still tolerable.
As a noun or suffix (〜増し), it indicates an increase or extra amount (e.g., 100円増し = an extra 100 yen).
この席は窓側で500円増しです。
This seat by the window costs an extra 500 yen.
このバッグは革製で、同じモデルよりも1000円増しだ。
This bag is leather and is 1,000 yen more than the same model.
An archaic noun meaning increase or growth. Rarely used in modern Japanese.
古い文献には『産業の増し』という表現が見られる。
In old documents you can see the expression '産業の増し' (increase of industry).