I have written a lot of things in my life, but this year it has become clear to me that I only have one story to tell. That thing is often in disguise – maybe it’s a political article, maybe it’s a cookbook, maybe it’s a collection of poetry – but I’m writing the same thing, over and over again.

It’s this: it’s nice to have a friend.

I’ve never written anything that wasn’t really about the pure joy of meeting someone who gets it and gets you. In everything I ever write I’m trying to articulate why friends are so good, and why we devalue friendship in favour of other kinds of relationship, and how all relationships are more complicated and beautiful and boundless than the labels we stick on them.

The word “friend” has to cover all manner of sins. It has to mean that girl you work with, but don’t want to offend; a mutual Twitter follower you’ve never met, but speak to every day; the flatmate who makes you toast every morning. It’s the same word for someone you’ve just met as for someone who has known you your whole life; it’s the same word for somebody you kind of like as for somebody without whom you feel like you might die. We just don’t have the vocab because, culturally speaking, we don’t really believe that friendship matters.

“We’re just friends,” we say, of someone we love dearly, but aren’t sleeping with. “Just friends, nothing more,” as if friendship were a sort of place on the road to monogamous sex-on-tap. Because we’re obsessed with couples, with The One. The One is Friendship Plus. The One is the most evolved Pokémon of love. This is, when you think about it, a profoundly curious idea: a real multiple-egg-single- basket distribution error.

I didn’t used to think like this. Even with my flexible definitions of family, expanding and contracting depending on who was around, I was pretty sure that it was just a question of finding the right One. I thought that with the right One, I’d do it all properly. Nuclear family with all the bits correctly labelled, like a diagram in a science textbook.

And then, you see, I met him. He was – and I am unbiased here – really something. He was a smasher. He was funny and mean and beautiful and clever, and I absolutely worshipped him, and then he died.

There’s a bit in the 2002 classic About a Boy that I think about all the time. A thing that tiny Nicholas Hoult in his woolly hat says, just after his mum Toni Collette tries to kill herself. He says, “That’s when I realised: two people isn’t enough. You’ve got to have backup. If there are only two people, and one of you drops off the edge, you’re on your own.”

My person, the writer John Underwood, dropped off the edge by degrees. He had cancer, to start with; then he acquired a brain injury; and then he died.

The thing about his getting ill was this: he got sick at exactly the wrong age. We were the wrong age. I was just 22, he was 25, 25 is a year too old for the young person’s cancer unit, where they have PlayStations and support networks; but much too young for the “how to tell your children you have cancer” and “mortgage support” leaflets.

Perhaps if we’d been just a bit older, we’d have had a house and kids and a marriage certificate of our own, and if we’d have been just a bit younger, we’d have gone home to our parents and been kids again ourselves. But we were who we were, and we had what we had, and what we had was each other. We had each other, and our friends.

“Friends are the family you choose” is a trite statement, but I watched as it became true. In the mad world of John’s sickness, friendship became to us something as important as any blood relationship, something as vital and meaningful and profound as any romantic relationship.

Other people our age were bonding over nights out and drinking and occasional trips to A&E. Other people our age never thought about blood counts or sperm banks or any other bodily fluids outside the context of a sexual health clinic. Other people our age lived in a world that seemed entirely distinct from ours, like two pieces of acetate laid over each other. I used to come out of the hospital and stare at people in pubs on my way home, baffled it could be Friday and baffled that Friday meant something still.

It must be said that we were a pretty close-knit friendship group before my partner had cancer. We did elaborate birthday treats and dinners that went on until well past the last tube. We talked a lot. We walked a lot. We lay around on the sofa, drinking red wine and playing the guitar, like people from films. If this sounds romantic, it’s meant to: it was.

What else could you call it? I met Caroline at a party my first year in London; we locked eyes and fell hopelessly in love and knew we were best friends. A little while later we ran through the rain together, holding hands and laughing.

Harry – a work colleague of John, and a stranger to me – turned up an hour early to a dinner party I’d forgotten was happening; we started talking about music and pies and we’ve been doing that, pretty much, ever since.

Lily offered me a doughnut in a pub; Lettie asked me about a (cheerfully gaudy) statuette of Catherine of Aragon in my window; I ran into Cornelia’s arms outside the Gare du Nord on an unseasonally warm October day a decade ago now; I saw Katya in a queue and immediately texted a mutual friend to demand we be set up. In the romcom world, they call this a meet-cute. In the real world, we don’t have a vocabulary for meeting people we don’t want to sleep with. If I have a flexible definition of family, I also now have a flexible definition of romance. Which gives me a kind of freedom from overthinking things. Freedom to be different; to change and to grow and to evolve.

And in that way, once John was ill, our friendships became different. Our meet-cutes became real, profound, life-changing relationships. It was only then, when our world had fallen apart, that our friends became our family. We were forged in a kind of emotional fire, I suppose, and the word “friend” started to sound almost laughable. They were there, too. They were in the hospital with us; they were at the end of the phone at two in the morning. They were there for our birthdays and Christmases when we couldn’t go to our families for fear of being far from the hospital. They were there for celebratory dinners whenever his blood counts got better and commiseration drinks when things got awful again. They slept in our bed and on our sofa and sat in hospital cafés for hours until I had a minute. They smuggled guitars and expensive meatball sandwiches into sterile wards; folded laundry and answered emails and drove cars and were, in every sense, there.

Some of them I’d known for a long time; some I barely knew at all. If you said you’d been dating someone for a year, you’d imply a certain degree of seriousness; to say you’ve only been friends with someone for a year implies in some ways that you barely know them. But they were there, and they were family.

“Friend” seemed such a flimsy word to describe a person who had washed your clothes and helped you dress; a person who had driven you to the beach so that you could yell into the sea, and filled your fridge, and cleaned your sink; a person who had pushed squares of Marmite toast into your open mouth as if you were a baby bird; a person who had curled herself around you as you slept so that if you woke you wouldn’t feel the coldness of the space across the double bed. “Friend” didn’t carry the kind of weight we needed it to bear – it didn’t carry the heft of the burden at all. It didn’t carry the duty, the responsibility, the care. It did not carry the love. It’s hard to write about this in a way that doesn’t feel fragile or melodramatic or saccharine: we don’t have the language.

With Caroline, we went for “my sister”, often; sometimes “my wife”. Our friend Harry became our collective “wayward nephew”: it seemed easier than explaining the complex intricacies of our gentle co-dependence. A gang of women I adored became my “aunts”, sending hampers and cards and constant support. Mark was our “London Dad”; Lily mothered me and fed me fish fingers as she fed her own small daughter. The small daughter – our godchild – drew pictures.

They were there the whole time, and they were there after he died and we were all left, reeling. But I was not on my own. I was never on my own. We had lost a pillar of our family, but there were enough of us left to hold each other up.

“Maybe you will be worried about being alone now,” our godchild (seven) wrote to me carefully, after John died. “But, you are my family and you do not have to be!” This part was underlined twice, in red pen, with a ruler.

We are friends, my goddaughter and I, in that we talk about things that we both like (pictures of horses, Taylor Swift) and build Lego together and she tells me, cryptically, about the gossip from Year Four. But she’s right: we’re more than that. We’re family.

We’re family in the way my housemate Tash and I are family: we’re a household, technically speaking, because we share “at least one meal a day together” (what a lovely definition that is). But it’s more than that: she knows everything that happens to me, because she’s the one here. We have small domestic routines, and all the tiny intimacies that you learn when you live with someone. I make the tea; she makes the toast. I cook; she washes up.

“You sound… married,” someone remarked the other day, and I told Tash this over dinner and we agreed it made sense. I don’t think we’re alone in this kind of non- marital domestic set-up: every week I hear about women living together to raise their children, or someone living with his adopted granny, or some other kind of non-nuclear communal living. “I used to think two wasn’t enough,” Nicholas Hoult also says, at the end of About a Boy, looking around at his new, chaotic life full of relationships that are impossible to articulate. “And now there were loads of people. I don’t think couples are the future. You need more than that. You need back-up.”

I see tiny signs that we might be moving collectively away from that cultural burden of The One: queer culture in particular has taught me a great deal about perceptions of love. I like this; I hope it means that one day we’ll have the language to explain it. But until then, I’ll keep looking. I’ll keep trying to articulate it, keep writing 2,000 words to try and say it better. For now, though, I’ll just keep flying this flag: it’s nice to have a friend.

Midnight Chicken and Other Recipes Worth Living For by Ella Risbridger and Elisa Cunningham (Bloomsbury, £22). Buy it for £19.36 from guardianbookshop.com