Threshhold is a common misspelling.
The correct spelling is threshold with no double h.
A threshold is a border between rooms that you walk over to change from one area to another. Another, more figurative, definition is that a threshold can be the moment when some quality or amount begins to change. This can be either a physical or psychological quality. The change can also mean that a condition is met when something goes above the threshold and another action can take place.
As we step over the threshold, I take care to check my straight-shooting self at the curb. [The Denver Post]
This mechanism is one of the main reasons that people with high blood pressure tend to have a higher pain threshold. [Express]
The National Wages Council changes the threshold for low-wage workers to those earning S$1,100 or less a month, and recommends a minimum S$60 built-in wage increase for low-wage workers. [Channel News Asia]
Many parents are finding out that this means it is difficult to pass on their properties to their children without lumbering them with a big bill. This is because the thresholds where the tax applies are so low, and the rate of the tax is so high. [Irish Independent]
Kevin Reid, project manager for Mayor Boris Johnson’s Drain London program, says he’s working with boroughs, schools and hospitals to make them aware of risks and preventive steps, even simple ones such as putting basement generators on platforms, raising door thresholds and stocking up on sandbags. [Bloomberg]