"What is love" was the most searched phrase on Google in 2012, according to the company. In an attempt to get to the bottom of the question once and for all, the Guardian has gathered writers from the fields of science, psychotherapy, literature, religion and philosophy to give their definition of the much-pondered word.

The physicist: 'Love is chemistry'

Biologically, love is a powerful neurological condition like hunger or thirst, only more permanent. We talk about love being blind or unconditional, in the sense that we have no control over it. But then, that is not so surprising since love is basically chemistry. While lust is a temporary passionate sexual desire involving the increased release of chemicals such as testosterone and oestrogen, in true love, or attachment and bonding, the brain can release a whole set of chemicals: pheromones, dopamine, norepinephrine, serotonin, oxytocin and vasopressin. However, from an evolutionary perspective, love can be viewed as a survival tool – a mechanism we have evolved to promote long-term relationships, mutual defence and parental support of children and to promote feelings of safety and security.

• Jim Al-Khalili is a theoretical physicist and science writer

The psychotherapist: 'Love has many guises'

Unlike us, the ancients did not lump all the various emotions that we label "love" under the one word. They had several variations, including:

Philia which they saw as a deep but usually non-sexual intimacy between close friends and family members or as a deep bond forged by soldiers as they fought alongside each other in battle. Ludus describes a more playful affection found in fooling around or flirting. Pragma is the mature love that develops over a long period of time between long-term couples and involves actively practising goodwill, commitment, compromise and understanding. Agape is a more generalised love, it's not about exclusivity but about love for all of humanity. Philautia is self love, which isn't as selfish as it sounds. As Aristotle discovered and as any psychotherapist will tell you, in order to care for others you need to be able to care about yourself. Last, and probably least even though it causes the most trouble, eros is about sexual passion and desire. Unless it morphs into philia and/or pragma, eros will burn itself out.

Love is all of the above. But is it possibly unrealistic to expect to experience all six types with only one person. This is why family and community are important.

• Philippa Perry is a psychotherapist and author of Couch Fiction

The philosopher: 'Love is a passionate commitment'

The answer remains elusive in part because love is not one thing. Love for parents, partners, children, country, neighbour, God and so on all have different qualities. Each has its variants – blind, one-sided, tragic, steadfast, fickle, reciprocated, misguided, unconditional. At its best, however, all love is a kind a passionate commitment that we nurture and develop, even though it usually arrives in our lives unbidden. That's why it is more than just a powerful feeling. Without the commitment, it is mere infatuation. Without the passion, it is mere dedication. Without nurturing, even the best can wither and die.

• Julian Baggini is a philosopher and writer

The romantic novelist: 'Love drives all great stories'

What love is depends on where you are in relation to it. Secure in it, it can feel as mundane and necessary as air – you exist within it, almost unnoticing. Deprived of it, it can feel like an obsession; all consuming, a physical pain. Love is the driver for all great stories: not just romantic love, but the love of parent for child, for family, for country. It is the point before consummation of it that fascinates: what separates you from love, the obstacles that stand in its way. It is usually at those points that love is everything.

• Jojo Moyes is a two-time winner of the Romantic Novel of the Year award

The nun: 'Love is free yet binds us'

Catherine Wybourne Photograph: Catherine Wybourne

Love is more easily experienced than defined. As a theological virtue, by which we love God above all things and our neighbours as ourselves for his sake, it seems remote until we encounter it enfleshed, so to say, in the life of another – in acts of kindness, generosity and self-sacrifice. Love's the one thing that can never hurt anyone, although it may cost dearly. The paradox of love is that it is supremely free yet attaches us with bonds stronger than death. It cannot be bought or sold; there is nothing it cannot face; love is life's greatest blessing.

• Catherine Wybourne is a Benedictine nun