When it comes to industries that offer entrepreneurs big opportunities, they often fall into the following categories: they're highly fragmented, outdated, or just generally reviled. Sometimes they're all three. 

The industries below are, accordingly, ready for big changes. One of the surest signs? Several innovative, well-funded startups already have taken notice and are busy muscling their way in with products and services designed to change the status quo. 

Here are five industries--and their disruptive startups--to watch in 2018.

1. Insurance

Just about everybody needs insurance, but few people get excited about it: The health insurance industry consistently lands near the bottom of the American Customer Satisfaction Index, and life and property insurance companies aren't exactly known for their ability to inspire. This is driven in part by difficult-to-understand policies and low levels of customer trust.

A new crop of startups is trying to solve that problem. Oscar, which offers health insurance policies that are easier to understand within a user-friendly app-based interface, has raised a reported $727 million in funding since 2013, though the company has failed to generate a profit and faces a murky future thanks to the uncertainty surrounding Obamacare. Property insurance startup Lemonade has tried to create a level of trust not usually found in the industry by using a business model in which it has nothing to gain monetarily by denying a person's claim. The startup targets renters, a population that is currently about 60 percent uninsured in the U.S.--and a potential market of nearly 65 million people. Insurance is heavily regulated and requires a lot of capital, so the barriers to entry are high--but there are opportunities to be had.

2. Weddings

The U.S. wedding industry grew to $76 billion in 2017, up from $72 billion the previous year, according to market research firm IBIS World. But an interesting trend is growing: Americans are spending less on wedding planners than they did five years ago, instead opting to customize their events and choose caterers, bartenders, DJs, and other vendors themselves. 

Consider how time-consuming that process is, and couple it with the fact that younger, more tech-savvy demographics are getting hitched, and you have an industry that is ripe for new tools and services. Existing wedding-related companies have already started consolidating various aspects of the planning experience: The Knot's app includes 300,000 vendors, and users can easily assess, contact, and book them from within it. Another startup, Joy, lets hosts manage their guest lists and sends notifications to invitees who haven't yet RSVP'd. Americans throw more than 2 million weddings per year, so there's room for other startups to help usher the industry into the 21st century.

3. Classroom education  

As schools transition away from paper, textbooks, and projectors, there's a growing opportunity for startups to create new tools geared toward educators. Perhaps not surprisingly, VC funding for ed-tech startups was estimated to approach $3 billion last year, according to CB Insights

Startups are already helping transform different aspects of the educational process. Schoology, which has secured a reported $57 million in funding, creates a platform for teachers, parents, and students to review work and communicate with one another. Newsela uses artificial intelligence to transform news articles into age-appropriate reading comprehension materials--and since its 2012 founding has already made its way into three-fourths of America's schools. And Examity, a startup that helps administer online tests while preventing cheating, closed a $21 million round last year and has partnerships with more than 100 universities. 

4. Health screening

Doctors generally do a great job of diagnosing patients. But artificial intelligence might soon be able to do it even better. Last year, a machine vision program developed by Stanford researchers was able to distinguish between cancerous and non-cancerous moles with more than 90 percent accuracy, beating out its human dermatologist counterparts--possibly a sign of what's to come in the field of AI.

Freenome, a liquid biopsy startup that's looking to enter clinical trials, is working on technology that would be able to detect cancer in the body, including its location and type, using only blood samples. Grail, a spinout from biotech giant Illumina, last year closed a $900 million round that included Amazon and Johnson & Johnson for its own early-stage cancer detection system. And startup Arterys, which uses machine learning to study MRI scans and detect abnormalities, recently became the first company to receive FDA approval for a cloud-based screening platform. Of course, doctors aren't going to lose their jobs anytime soon--many of these companies position their products as being used to supplement clinicians instead of replacing them.

5. Law

Getting legal advice is expensive. Thanks to artificial intelligence, though, that might not be the case for long. As AI becomes more and more capable of processing and understanding complex language, lawyers' jobs are becoming more efficient. Casetext, which was founded in 2013 and closed a $12 million round last year, has developed software that can read a brief and suggest relevant past cases in a matter of seconds. Other companies, like LawGeex, offer platforms that can examine written contracts for missing information, troublesome language, or other potential red flags. Don't be surprised if soon you might be able to ask a chat bot for specific legal advice.