According to the Edward Lowe Foundation, second-stage firms typically have revenue between $1 million and $50 million and 10 to 100 employees. They are described as firms "that have grown past the startup stage but have not grown to maturity."
PS:The Edward Lowe Foundation conducts educational programs and provides information and recognition for second-stage entrepreneurs.

楼上仁兄，这个不用我翻译了吧！就是摆脱了起步阶段，但没没成熟的企业罢了，有一些收入、雇员的标准罢了！

“第二阶段的公司”有很强的成长性，有很强的战略需求，例如领导力的发展、管理团队的构建、战略规划、市场机会发掘和变革产业等。相较于成立初期的公司，不单单只是面对日常的运营管理（现金流、财务、简单物流）。

Characteristics of Second-Stage

Second-stage companies are those that have grown past the startup stage but have not grown to maturity. They have enough employees to exceed the comfortable control span of one owner/CEO and benefit from adding professional managers, but they do not yet have a full-scale professional management team.

A business typically begins to enter its second stage when it approaches $1 million in total receipts. The transition process can continue until it hits $100 million in receipts, although for most companies $50 million represents the upper limit of second stage. By $100 million, a firm will have to be professionally managed in order to continue to thrive and grow and be in its third stage of development. Employee numbers and revenue ranges vary by industry, but the population of firms with 10 to 100 employees and/or $750,000 to $50 million in receipts includes the vast majority of second-stage companies.

Here are a few of the many signs identified by Eric Flamholtz and Yvonne Randle1 that indicate to a CEO that second stage is at hand:

Many people are not aware of what others are doing.
People lack an understanding of the firm's ultimate goals.
A precipitous drop in product quality occurs for unknown reasons.
Turnover increases sharply, just when the company needs more personnel.
You wake up worrying about operational tasks that someone else ought to be handling.
All your customers want to meet with you, but finding the time to do so seems impossible.